ci: build examples on windows-prebuilt

.github/workflows/ci.yml

@@ -173,7 +173,7 @@ jobs:
         ./v.exe --version
         echo "Done"
     - name: Test V
-      run: echo "test" #./v.exe examples/hello_world.v && examples/hello_world.exe
+      run: ./v.exe examples/hello_world.v && examples/hello_world.exe && ./v.exe build-examples
 
   ubuntu-musl:
     runs-on: ubuntu-18.04