CI: fix MSVC builds when building dependencies

Author: triplef

.github/workflows/main.yml

@@ -240,10 +240,21 @@ jobs:
           # make Windows packages like Clang available in MSYS
           path-type: inherit
 
-      - name: Delete MinGW gmake (MSVC)
-        if: env.IS_WINDOWS_MSVC == 'true'
-        # delete /c/Strawberry/c/bin/gmake built for MinGW that is found on runners, because we must use make built for MSYS
-        run: if GMAKE_PATH=`which gmake`; then rm -f "$GMAKE_PATH"; fi
+      - name: Remove Perl Strawberry installation and MinGW gmake (MSVC)
+        if: env.IS_WINDOWS_MSVC == 'true' && github.event.inputs.tools_windows_msvc_branch
+        # C:\Strawberry contains various MinGW libraries and binaries like pkg-config
+        # that can get picked up by configure/CMake and don't necessarily behave
+        # correctly when not using a MinGW environment, and more specifically we cannot
+        # use MinGW gmake (we must use MSYS make), so we delete everything that could
+        # mess up our builds
+        run: |
+          echo Deleting C:\Strawberry...
+          rmdir /S /Q C:\Strawberry
+          for /f "delims=" %%i in ('where gmake') do (
+            echo Deleting "%%~i"...
+            del "%%~i"
+          )
+        shell: cmd
 
       - name: Install Windows packages (MSVC)
         if: env.IS_WINDOWS_MSVC == 'true'