Fix Windows CI errors not failing the build

.github/workflows/ci.yml

@@ -51,6 +51,7 @@ jobs:
           tar -xf SDL2-devel-2.0.12-VC.zip
           mv SDL2-2.0.12 SDL2
       - name: build sowon
+        shell: cmd
         run: |
           ./build_msvc.bat
   build-freebsd: