change shell

Author: diegorusso

.github/workflows/reusable-windows-msi.yml

@@ -31,4 +31,5 @@ jobs:
       with:
         persist-credentials: false
     - name: Build CPython installer
-      run: ./Tools/msi/build.bat --doc -"${ARCH}"
+      run: ./Tools/msi/build.bat --doc -"%ARCH%"
+      shell: cmd