ci:macos: GCC needs Xcode 15.1

Author: scivision

.github/workflows/composite-unix/action.yml

@@ -17,6 +17,13 @@ runs:
       sudo apt update
       sudo apt install --no-install-recommends ninja-build
 
+  - name: MacoS GCC workaround
+    shell: bash
+    run: sudo xcode-select --switch /Applications/Xcode_15.1.app
+    if: runner.os == 'macOS' && ${{ env.CC == 'gcc-13' }}
+    # https://docs.brew.sh/Xcode
+    # https://github.com/Homebrew/brew/blob/HEAD/Library/Homebrew/os/mac/xcode.rb#L20
+
   - run: cmake --preset multi
     shell: bash