diff --git a/images/extension-builders/entrypoint.sh b/images/extension-builders/entrypoint.sh
index d5dba9f7..a4af04cb 100755
--- a/images/extension-builders/entrypoint.sh
+++ b/images/extension-builders/entrypoint.sh
@@ -14,25 +14,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-set -e
+set -ue
 
 SCRIPT_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}")"  && pwd)
-GETENVOY_WORKSPACE_DIR="${GETENVOY_WORKSPACE_DIR:-$PWD}"
 
-USAGE="usage: build [--output-file PATH]
+# Note: we are using option syntax for --output-file even if this was always required. This is for compatibility with
+# older versions of the getenvoy binary.
+USAGE="usage: build --output-file path/to/extension.wasm
    or: test
    or: clean
 
 examples:
-   # build Wasm extension (location of *.wasm file is undefined)
-   build
-
    # build Wasm extension and copy *.wasm file to a given location
    build --output-file target/extension.wasm
-
-options:
-   build:
-   --output-file PATH   Path relative to the workspace root to copy *.wasm file to
 "
 
 usage() {
diff --git a/images/extension-builders/rust/Dockerfile b/images/extension-builders/rust/Dockerfile
index e71d0166..0ac4d130 100644
--- a/images/extension-builders/rust/Dockerfile
+++ b/images/extension-builders/rust/Dockerfile
@@ -19,9 +19,9 @@ FROM rust:1.44.1
 
 RUN rustup target add wasm32-unknown-unknown
 
-# Unset CARGO_HOME. This way we will be able to determine when a user
-# provides an override value.
+# Unset CARGO_HOME and CARGO_TARGET_DIR. This way we will know when a user overrides them.
 ENV CARGO_HOME=
+ENV CARGO_TARGET_DIR=
 
 COPY ./entrypoint.sh /usr/local/getenvoy/extension/builder/entrypoint.sh
 COPY ./rust/commands.sh /usr/local/getenvoy/extension/builder/commands.sh
diff --git a/images/extension-builders/rust/commands.sh b/images/extension-builders/rust/commands.sh
index a777028b..3a468f41 100755
--- a/images/extension-builders/rust/commands.sh
+++ b/images/extension-builders/rust/commands.sh
@@ -13,31 +13,75 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+set -ue
 
-# Ensure location of the build directory.
-export CARGO_TARGET_DIR="${CARGO_TARGET_DIR:-${GETENVOY_WORKSPACE_DIR}/target}"
+export CARGO_TARGET="wasm32-unknown-unknown"
 
-# Keep Cargo cache inside the build directory, unless a user explicitly
-# overrides CARGO_HOME.
-export CARGO_HOME="${CARGO_HOME:-${CARGO_TARGET_DIR}/.cache/getenvoy/extension/rust-builder/cargo}"
+# Ensure location of the build cache directory.
+# See https://doc.rust-lang.org/cargo/guide/build-cache.html
+export CARGO_TARGET_DIR=${CARGO_TARGET_DIR:-${PWD}/target}
+
+# Keep Cargo cache inside the build directory, unless a user explicitly overrides CARGO_HOME.
+# See https://doc.rust-lang.org/cargo/guide/cargo-home.html
+export CARGO_HOME=${CARGO_HOME:-${CARGO_TARGET_DIR}/.cache/getenvoy/extension/rust-builder/cargo}
+
+# This is used in macOS, where we build in temporary directories. We only cache minimum as copying is slow.
+# See https://doc.rust-lang.org/cargo/guide/cargo-home.html#caching-the-cargo-home-in-c
+copy_cargo_home_cache() {
+	source_dir=${1}
+	dest_dir=${2}
+
+	# See if there is anything to copy
+	dirs=""
+	for dir in bin registry/index registry/cache git/db; do
+		test -d "${source_dir}/$dir" && dirs="$dirs $dir"
+	done
+
+	# If any directory existed, copy them to the destination
+	if [ -n "$dirs" ]; then
+		mkdir -p "${dest_dir}" 2>&- || true
+		log_message "     Copying cacheable dirs $dirs from ${source_dir} to ${dest_dir}"
+		(
+			cd "${source_dir}"
+			tar -cpf - $dirs | (
+				cd "${dest_dir}"
+				tar -xpf -
+			)
+		)
+	fi
+}
 
 #########################################################################
 # Build Wasm extension and copy *.wasm file to a given location.
 # Globals:
+#   CARGO_HOME
 #   CARGO_TARGET_DIR
-#   GETENVOY_WORKSPACE_DIR
+#   GETENVOY_GOOS
 # Arguments:
 #   Path relative to the workspace root to copy *.wasm file to.
 #########################################################################
-extension_build()  {
-	local target="wasm32-unknown-unknown"
+extension_build() {
+	# Avoid slow IO problems when the Docker host is macOS and bind-mounted volumes. We do this by building into a
+	# temp directory, copying back cacheable contents later.
+	if [ "${GETENVOY_GOOS:-}" == "darwin" ]; then
+		REAL_CARGO_HOME=${CARGO_HOME}
+		export CARGO_HOME=/tmp/$$-cargo
+		copy_cargo_home_cache "${REAL_CARGO_HOME}" "${CARGO_HOME}"
+
+		export CARGO_TARGET_DIR=/tmp/$$-build
+		# We don't copy revert the updated target dir back to the original location because the copying is slower than
+		# recompiling each time.
+	fi
+
+	mkdir -p "${CARGO_HOME}" 2>&- || true
+	mkdir -p "${CARGO_TARGET_DIR}" 2>&- || true
 
-	cargo build --target "${target}"
+	cargo build --target "${CARGO_TARGET}"
 
 	local profile="debug"
 	local lib_name="extension"
 	local file_name="${lib_name}.wasm"
-	local cargo_output_file="${CARGO_TARGET_DIR}/${target}/${profile}/${file_name}"
+	local cargo_output_file="${CARGO_TARGET_DIR}/${CARGO_TARGET}/${profile}/${file_name}"
 
 	if [[ ! -f "${cargo_output_file}" ]]; then
 		error "Cargo didn't build a *.wasm file at expected location: ${cargo_output_file}.
@@ -53,22 +97,21 @@ help:  make sure Cargo workspace includes a library crate with name '${lib_name}
 "
 	fi
 
-	local destination_file="$1"
-	if [[ -n "${destination_file}" ]]; then
-		log_message "     Copying *.wasm file to '${destination_file}'"
+	local destination_file="${PWD}/$1"
+	log_message "     Copying *.wasm file to '${destination_file}'"
+	mkdir -p "$(dirname "${destination_file}")"
+	cp "${cargo_output_file}" "${destination_file}"
 
-		destination_file="${GETENVOY_WORKSPACE_DIR}/${destination_file}"
-		local tmp_file="${destination_file}.tmp"
-		mkdir -p "$(dirname "${tmp_file}")"
-		cp "${cargo_output_file}" "${tmp_file}"
-		mv "${tmp_file}" "${destination_file}"
+	if [ "${GETENVOY_GOOS:-}" == "darwin" ]; then
+		copy_cargo_home_cache "${CARGO_HOME}" "${REAL_CARGO_HOME}"
+		rm -rf /tmp/$$*
 	fi
 }
 
-extension_test()  {
+extension_test() {
 	cargo test
 }
 
-extension_clean()  {
+extension_clean() {
 	cargo clean
 }
diff --git a/images/extension-builders/tinygo/commands.sh b/images/extension-builders/tinygo/commands.sh
index f38e1273..6190839c 100755
--- a/images/extension-builders/tinygo/commands.sh
+++ b/images/extension-builders/tinygo/commands.sh
@@ -13,6 +13,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+set -ue
 
 extension_build()  {
 	tinygo build -o "$1" -scheduler=none -target wasi main.go
diff --git a/pkg/cmd/extension/build/cmd_test.go b/pkg/cmd/extension/build/cmd_test.go
index 10043be2..9456841b 100644
--- a/pkg/cmd/extension/build/cmd_test.go
+++ b/pkg/cmd/extension/build/cmd_test.go
@@ -17,6 +17,7 @@ package build_test
 import (
 	"fmt"
 	"os/user"
+	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -105,8 +106,8 @@ func TestGetEnvoyExtensionBuild(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect docker to run from the correct path, as the current user and mount a volume for the correct workspace.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
-		dockerDir, expectedUser.Uid, expectedUser.Gid, workspaceDir)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
+		dockerDir, expectedUser.Uid, expectedUser.Gid, runtime.GOOS, workspaceDir)
 
 	// Verify the command invoked, passing the correct default commandline
 	require.NoError(t, err, `expected no error running [%v]`, c)
@@ -161,8 +162,8 @@ func TestGetEnvoyExtensionBuildFail(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect the exit instruction to have gotten to the fake docker script, along with the default options.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
-		dockerDir, expectedUser.Uid, expectedUser.Gid, workspaceDir, toolchainOptions)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
+		dockerDir, expectedUser.Uid, expectedUser.Gid, runtime.GOOS, workspaceDir, toolchainOptions)
 
 	// Verify the command failed with the expected error.
 	expectedErr := fmt.Sprintf(`failed to build Envoy extension using "default" toolchain: failed to execute an external command "%s": exit status 3`, expectedDockerExec)
diff --git a/pkg/cmd/extension/clean/cmd_test.go b/pkg/cmd/extension/clean/cmd_test.go
index 9e2288c4..3aa7bc16 100644
--- a/pkg/cmd/extension/clean/cmd_test.go
+++ b/pkg/cmd/extension/clean/cmd_test.go
@@ -17,6 +17,7 @@ package clean_test
 import (
 	"fmt"
 	"os/user"
+	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -105,8 +106,8 @@ func TestGetEnvoyExtensionClean(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect docker to run from the correct path, as the current user and mount a volume for the correct workspace.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest clean",
-		dockerDir, expectedUser.Uid, expectedUser.Gid, workspaceDir)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest clean",
+		dockerDir, expectedUser.Uid, expectedUser.Gid, runtime.GOOS, workspaceDir)
 
 	// Verify the command invoked, passing the correct default commandline
 	require.NoError(t, err, `expected no error running [%v]`, c)
@@ -161,8 +162,8 @@ func TestGetEnvoyExtensionCleanFail(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect the exit instruction to have gotten to the fake docker script, along with the default options.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest clean",
-		dockerDir, expectedUser.Uid, expectedUser.Gid, workspaceDir, toolchainOptions)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest clean",
+		dockerDir, expectedUser.Uid, expectedUser.Gid, runtime.GOOS, workspaceDir, toolchainOptions)
 
 	// Verify the command failed with the expected error.
 	expectedErr := fmt.Sprintf(`failed to clean build directory of Envoy extension using "default" toolchain: failed to execute an external command "%s": exit status 3`, expectedDockerExec)
diff --git a/pkg/cmd/extension/run/cmd_test.go b/pkg/cmd/extension/run/cmd_test.go
index 87bb8df0..6dbafe3c 100644
--- a/pkg/cmd/extension/run/cmd_test.go
+++ b/pkg/cmd/extension/run/cmd_test.go
@@ -20,6 +20,7 @@ import (
 	"os"
 	"os/user"
 	"path/filepath"
+	"runtime"
 	"testing"
 
 	"github.com/Masterminds/semver"
@@ -169,11 +170,11 @@ func TestGetEnvoyExtensionRun(t *testing.T) {
 	envoyWd := cmd.ParseEnvoyWorkDirectory(stdout)
 
 	// We expect docker to build from the correct path, as the current user and mount a volume for the correct workspace.
-	expectedStdout := fmt.Sprintf(`%s/docker run -u %s --rm -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm
+	expectedStdout := fmt.Sprintf(`%s/docker run -u %s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm
 envoy pwd: %s
 envoy bin: %s
 envoy args: -c %s/envoy.tmpl.yaml`,
-		config.dockerDir, config.expectedUidGid, config.workspaceDir, envoyWd, envoyBin, envoyWd)
+		config.dockerDir, config.expectedUidGid, runtime.GOOS, config.workspaceDir, envoyWd, envoyBin, envoyWd)
 	require.Equal(t, expectedStdout+"\n", stdout.String(), `expected stdout running [%v]`, c)
 	require.Equal(t, "docker stderr\nenvoy stderr\n", stderr.String(), `expected stderr running [%v]`, c)
 
@@ -199,8 +200,8 @@ func TestGetEnvoyExtensionRunDockerFail(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect the exit instruction to have gotten to the fake docker script, along with the default options.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s --rm -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
-		config.dockerDir, config.expectedUidGid, config.workspaceDir, toolchainOptions)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
+		config.dockerDir, config.expectedUidGid, runtime.GOOS, config.workspaceDir, toolchainOptions)
 
 	// Verify the command failed with the expected error.
 	expectedErr := fmt.Sprintf(`failed to build Envoy extension using "default" toolchain: failed to execute an external command "%s": exit status 3`, expectedDockerExec)
diff --git a/pkg/cmd/extension/test/cmd_test.go b/pkg/cmd/extension/test/cmd_test.go
index 1e7cba07..14bef7ae 100644
--- a/pkg/cmd/extension/test/cmd_test.go
+++ b/pkg/cmd/extension/test/cmd_test.go
@@ -17,6 +17,7 @@ package test_test
 import (
 	"fmt"
 	"os/user"
+	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -105,8 +106,8 @@ func TestGetEnvoyExtensionTest(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect docker to run from the correct path, as the current user and mount a volume for the correct workspace.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
-		dockerDir, expectedUser.Uid, expectedUser.Gid, workspaceDir)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init getenvoy/extension-rust-builder:latest build --output-file target/getenvoy/extension.wasm",
+		dockerDir, expectedUser.Uid, expectedUser.Gid, runtime.GOOS, workspaceDir)
 
 	// Verify the command invoked, passing the correct default commandline
 	require.NoError(t, err, `expected no error running [%v]`, c)
@@ -161,8 +162,8 @@ func TestGetEnvoyExtensionTestFail(t *testing.T) {
 	err := cmdutil.Execute(c)
 
 	// We expect the exit instruction to have gotten to the fake docker script, along with the default options.
-	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest test",
-		dockerDir, expectedUser.Uid, expectedUser.Gid, workspaceDir, toolchainOptions)
+	expectedDockerExec := fmt.Sprintf("%s/docker run -u %s:%s --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init %s getenvoy/extension-rust-builder:latest test",
+		dockerDir, expectedUser.Uid, expectedUser.Gid, runtime.GOOS, workspaceDir, toolchainOptions)
 
 	// Verify the command failed with the expected error.
 	expectedErr := fmt.Sprintf(`failed to unit test Envoy extension using "default" toolchain: failed to execute an external command "%s": exit status 3`, expectedDockerExec)
diff --git a/pkg/extension/workspace/toolchain/builtin/toolchain.go b/pkg/extension/workspace/toolchain/builtin/toolchain.go
index ab0a3b8e..00141143 100644
--- a/pkg/extension/workspace/toolchain/builtin/toolchain.go
+++ b/pkg/extension/workspace/toolchain/builtin/toolchain.go
@@ -19,6 +19,7 @@ import (
 	"os/exec"
 	"os/user"
 	"path/filepath"
+	"runtime"
 
 	config "github.com/tetratelabs/getenvoy/pkg/extension/workspace/config/toolchain/builtin"
 	"github.com/tetratelabs/getenvoy/pkg/extension/workspace/model"
@@ -97,6 +98,7 @@ func (t *builtin) dockerCliArgs(container *config.ContainerConfig) (executil.Arg
 		"run",
 		"-u", fmt.Sprintf("%s:%s", u.Uid, u.Gid), // to get proper ownership on files created by the container
 		"--rm",
+		"-e", "GETENVOY_GOOS=" + runtime.GOOS, // Allows builder images to act based on execution env
 		"-t", // to get interactive/colored output out of container
 		"-v", fmt.Sprintf("%s:%s", t.workspace.GetDir().GetRootDir(), "/source"),
 		"-w", "/source",
diff --git a/pkg/extension/workspace/toolchain/builtin/toolchain_test.go b/pkg/extension/workspace/toolchain/builtin/toolchain_test.go
index 95438108..c7c231ea 100644
--- a/pkg/extension/workspace/toolchain/builtin/toolchain_test.go
+++ b/pkg/extension/workspace/toolchain/builtin/toolchain_test.go
@@ -22,6 +22,7 @@ import (
 	"os"
 	"os/user"
 	"path/filepath"
+	"runtime"
 	"strings"
 
 	. "github.com/onsi/ginkgo"
@@ -152,7 +153,7 @@ var _ = Describe("built-in toolchain", func() {
                   image: default/image
 `,
 				tool:           build,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init default/image build --output-file extension.wasm\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init default/image build --output-file extension.wasm\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("test using default container image", func() testCase {
@@ -163,7 +164,7 @@ var _ = Describe("built-in toolchain", func() {
                   image: default/image
 `,
 				tool:           test,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init default/image test\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init default/image test\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("clean using default container image", func() testCase {
@@ -174,7 +175,7 @@ var _ = Describe("built-in toolchain", func() {
                   image: default/image
 `,
 				tool:           clean,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init default/image clean\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init default/image clean\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("build using given container image", func() testCase {
@@ -194,7 +195,7 @@ var _ = Describe("built-in toolchain", func() {
                     image: test/image
 `,
 				tool:           build,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init build/image build --output-file output/file.wasm\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init build/image build --output-file output/file.wasm\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("build using given container image and Docker cli options", func() testCase {
@@ -220,7 +221,7 @@ var _ = Describe("built-in toolchain", func() {
                     - /host/path=/container/path
 `,
 				tool:           build,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e VAR=VALUE build/image build --output-file output/file.wasm\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e VAR=VALUE build/image build --output-file output/file.wasm\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("build fails with a non-0 exit code", func() testCase {
@@ -239,8 +240,8 @@ var _ = Describe("built-in toolchain", func() {
                     wasmFile: output/file.wasm
 `,
 				tool:           build,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 build/image build --output-file output/file.wasm\n", workspace.GetDir().GetRootDir()),
-				expectedErr:    fmt.Sprintf("failed to execute an external command \"testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 build/image build --output-file output/file.wasm\": exit status 3", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 build/image build --output-file output/file.wasm\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
+				expectedErr:    fmt.Sprintf("failed to execute an external command \"testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 build/image build --output-file output/file.wasm\": exit status 3", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("test using given container image", func() testCase {
@@ -260,7 +261,7 @@ var _ = Describe("built-in toolchain", func() {
                     image: test/image
 `,
 				tool:           test,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init test/image test\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init test/image test\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("test using given container image and Docker cli options", func() testCase {
@@ -286,7 +287,7 @@ var _ = Describe("built-in toolchain", func() {
                     - /host/path=/container/path
 `,
 				tool:           test,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -v /host/path=/container/path test/image test\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -v /host/path=/container/path test/image test\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("test fails with a non-0 exit code", func() testCase {
@@ -303,8 +304,8 @@ var _ = Describe("built-in toolchain", func() {
                     - DOCKER_EXIT_CODE=3
 `,
 				tool:           test,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 test/image test\n", workspace.GetDir().GetRootDir()),
-				expectedErr:    fmt.Sprintf("failed to execute an external command \"testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 test/image test\": exit status 3", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 test/image test\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
+				expectedErr:    fmt.Sprintf("failed to execute an external command \"testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 test/image test\": exit status 3", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("clean using given container image", func() testCase {
@@ -324,7 +325,7 @@ var _ = Describe("built-in toolchain", func() {
                     image: clean/image
 `,
 				tool:           clean,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init clean/image clean\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init clean/image clean\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("clean using given container image and Docker cli options", func() testCase {
@@ -350,7 +351,7 @@ var _ = Describe("built-in toolchain", func() {
                     - /host/path=/container/path
 `,
 				tool:           clean,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -v /host/path=/container/path clean/image clean\n", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -v /host/path=/container/path clean/image clean\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 		Entry("clean fails with a non-0 exit code", func() testCase {
@@ -367,8 +368,8 @@ var _ = Describe("built-in toolchain", func() {
                     - DOCKER_EXIT_CODE=3
 `,
 				tool:           clean,
-				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 clean/image clean\n", workspace.GetDir().GetRootDir()),
-				expectedErr:    fmt.Sprintf("failed to execute an external command \"testdata/toolchain/docker run -u 1001:1002 --rm -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 clean/image clean\": exit status 3", workspace.GetDir().GetRootDir()),
+				expectedStdOut: fmt.Sprintf("testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 clean/image clean\n", runtime.GOOS, workspace.GetDir().GetRootDir()),
+				expectedErr:    fmt.Sprintf("failed to execute an external command \"testdata/toolchain/docker run -u 1001:1002 --rm -e GETENVOY_GOOS=%s -t -v %s:/source -w /source --init -e DOCKER_EXIT_CODE=3 clean/image clean\": exit status 3", runtime.GOOS, workspace.GetDir().GetRootDir()),
 			}
 		}),
 	)