pref: fix cross-compiling graphical apps to Windows (#7449)

.github/workflows/ci.yml

@@ -153,6 +153,7 @@ jobs:
         brew install postgresql
         brew install glfw
         ## brew install sdl2 sdl2_ttf sdl2_mixer sdl2_image
+        brew install mingw-w64
         export LIBRARY_PATH="$LIBRARY_PATH:/usr/local/opt/openssl/lib/"
     - name: Build V
       run:  make -j4 && ./v -cg -cflags -Werror -o v cmd/v
@@ -189,7 +190,13 @@ jobs:
       run: |
         ./v doctor
     - name: Cross-compilation to Linux
-      run: ./v -os linux cmd/v
+      run: |
+        ./v -os linux cmd/v
+        # TODO: fix this: ./v -os linux examples/2048/2048.v
+    - name: Cross-compilation to Windows
+      run: |
+        ./v -os windows cmd/v
+        ./v -os windows examples/2048/2048.v
 #    - name: Test vsh
 #      run:  ./v examples/v_script.vsh
     - name: Test ved
@@ -576,6 +583,10 @@ jobs:
         ./v -os windows examples/hello_world.v
         ls -lart examples/hello_world.exe
         wine examples/hello_world.exe
+    - name: 2048.v can be cross compiled to 2048.exe
+      run: |
+        ./v -os windows examples/2048/2048.v
+        ls -lart examples/2048/2048.exe
 
   ubuntu-c-plus-plus:
     runs-on: ubuntu-18.04