CI: fix Windows

Author: cometkim

.github/workflows/ci.yml

@@ -273,6 +273,7 @@ jobs:
 
       - name: Delete stable compiler build state
         if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+        shell: bash
         run: |
           gh actions-cache delete ${{ steps.compiler-build-state-key.outputs.value }} \
             -R ${{ github.repository }} \