ci: Simplify tests for verbatim paths

Rather than setting an environment variable in the workflow job based on
whether or not the environment is non-MinGW Windows, we can just check
this in the ci script.

This was originally added in b0f1966 ("Add tests for UNC paths on
windows builds") and its followup commits.

Author: tgross35

.github/workflows/main.yaml

@@ -50,7 +50,6 @@ jobs:
           os: ubuntu-24.04-arm
         - target: aarch64-pc-windows-msvc
           os: windows-2025
-          test_verbatim: 1
           build_only: 1
         - target: arm-unknown-linux-gnueabi
           os: ubuntu-24.04
@@ -92,10 +91,8 @@ jobs:
           os: macos-13
         - target: i686-pc-windows-msvc
           os: windows-2025
-          test_verbatim: 1
         - target: x86_64-pc-windows-msvc
           os: windows-2025
-          test_verbatim: 1
         - target: i686-pc-windows-gnu
           os: windows-2025
           channel: nightly-i686-gnu
@@ -106,7 +103,6 @@ jobs:
     needs: [calculate_vars]
     env:
       BUILD_ONLY: ${{ matrix.build_only }}
-      TEST_VERBATIM: ${{ matrix.test_verbatim }}
       MAY_SKIP_LIBM_CI: ${{ needs.calculate_vars.outputs.may_skip_libm_ci }}
     steps:
     - name: Print $HOME

ci/run.sh

@@ -41,7 +41,10 @@ else
     "${test_builtins[@]}" --benches
     "${test_builtins[@]}" --benches --release
 
-    if [ "${TEST_VERBATIM:-}" = "1" ]; then
+    # Validate that having a verbatim path for the target directory works
+    # (trivial to regress using `/` in paths to build artifacts rather than
+    # `Path::join`). MinGW does not currently support these paths.
+    if [[ "$target" = *"windows"* ]] && [[ "$target" != *"gnu"* ]]; then
         verb_path=$(cmd.exe //C echo \\\\?\\%cd%\\builtins-test\\target2)
         "${test_builtins[@]}" --target-dir "$verb_path" --features c
     fi