improve rpi build

Author: electronstudio

.github/workflows/build.yml

@@ -215,6 +215,8 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
+        with:
+          submodules: recursive
 
       - name: Build raylib
         run: |