Use bin-dir override on setup_envtest

Rather than change XDG_DATA_HOME, since many distributions do not
explicitly define XDG_DATA_HOME but rather fallback to the default, use
a new optional variable SETUP_ENVTEST_BIN_DIR to override the
setup_envtest binary directory.

Signed-off-by: Tayler Geiger <tayler@redhat.com>

Makefile

@@ -12,10 +12,13 @@ export WAIT_TIMEOUT ?= 60s
 IMG?=$(IMAGE_REPO):$(IMAGE_TAG)
 TESTDATA_DIR := testdata
 
-# setup-envtest on *nix uses XDG_DATA_HOME, falling back to HOME, as the default storage directory. Some CI setups
-# don't have XDG_DATA_HOME set; in those cases, we set it here so setup-envtest functions correctly. This shouldn't
-# affect developers.
-export XDG_DATA_HOME ?= /tmp/.local/share
+# By default setup-envtest will write to $XDG_DATA_HOME, or $HOME/.local/share
+# if that is not defined. Set KUBEBUILDER_ASSETS_DIR to override.
+# Useful for some CI/CD environments that do not have or use the default $XDG_DATA_HOME.
+setup_envtest_bin_dir_override=
+ifdef SETUP_ENVTEST_BIN_DIR
+	setup_envtest_bin_dir_override += --bin-dir $(SETUP_ENVTEST_BIN_DIR)
+endif
 
 # bingo manages consistent tooling versions for things like kind, kustomize, etc.
 include .bingo/Variables.mk
@@ -125,7 +128,7 @@ test-ext-dev-e2e: $(SETUP_ENVTEST) $(OPERATOR_SDK) $(KUSTOMIZE) $(KIND) #HELP Ru
 ENVTEST_VERSION = $(shell go list -m k8s.io/client-go | cut -d" " -f2 | sed 's/^v0\.\([[:digit:]]\{1,\}\)\.[[:digit:]]\{1,\}$$/1.\1.x/')
 UNIT_TEST_DIRS=$(shell go list ./... | grep -v /test/)
 test-unit: $(SETUP_ENVTEST) #HELP Run the unit tests
-	eval $$($(SETUP_ENVTEST) use -p env $(ENVTEST_VERSION)) && go test -tags $(GO_BUILD_TAGS) -count=1 -short $(UNIT_TEST_DIRS) -coverprofile cover.out
+	eval $$($(SETUP_ENVTEST) use -p env $(ENVTEST_VERSION)) $(setup_envtest_bin_dir_override) && go test -tags $(GO_BUILD_TAGS) -count=1 -short $(UNIT_TEST_DIRS) -coverprofile cover.out
 
 E2E_REGISTRY_NAME=docker-registry
 E2E_REGISTRY_NAMESPACE=operator-controller-e2e