I think it needs the default part too

Author: nbollom

.github/workflows/cmake_windows.yml

@@ -8,6 +8,9 @@ jobs:
   build-macos:
     name: Windows
     runs-on: windows-latest
+    defaults:
+      run:
+        shell: msys2 {0}
     steps:
       - name: Checkout source
         uses: actions/checkout@v4