Add workaround for RUSTUP_WINDOWS_PATH_ADD_BIN.

On Windows, rustup has an issue with recursive cargo invocations. This
commit can be removed once
rust-lang/rustup#3036 is resolved.

.github/workflows/main.yml

@@ -116,6 +116,8 @@ jobs:
       CARGO_PROFILE_TEST_DEBUG: 1
       CARGO_INCREMENTAL: 0
       CARGO_PUBLIC_NETWORK_TESTS: 1
+      # Workaround for https://github.com/rust-lang/rustup/issues/3036
+      RUSTUP_WINDOWS_PATH_ADD_BIN: 0
     strategy:
       matrix:
         include:
@@ -170,7 +172,6 @@ jobs:
     - name: Configure extra test environment
       run: echo CARGO_CONTAINER_TESTS=1 >> $GITHUB_ENV
       if: matrix.os == 'ubuntu-latest'
-
     - run: cargo test -p cargo
     - name: Clear intermediate test output
       run: ci/clean-test-output.sh

crates/cargo-test-macro/src/lib.rs

@@ -248,6 +248,13 @@ fn has_rustup_stable() -> bool {
         // This cannot run on rust-lang/rust CI due to the lack of rustup.
         return false;
     }
+    if cfg!(windows) && !is_ci() && option_env!("RUSTUP_WINDOWS_PATH_ADD_BIN").is_none() {
+        // There is an issue with rustup that doesn't allow recursive cargo
+        // invocations. Disable this on developer machines if the environment
+        // variable is not enabled. This can be removed once
+        // https://github.com/rust-lang/rustup/issues/3036 is resolved.
+        return false;
+    }
     check_command("cargo", &["+stable", "--version"])
 }