CI: install libgl-dev in GitHub Actions

Author: garbear

.github/workflows/build.yml

@@ -31,6 +31,10 @@ jobs:
       run: |
         mkdir -p ${{ github.workspace }}/xbmc/cmake/addons/addons/${app_id}
         echo ${app_id} ${{ github.workspace }}/${app_id} > ${{ github.workspace }}/xbmc/cmake/addons/addons/${app_id}/${app_id}.txt
+    - name: Install GL deps
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y libgl-dev
     - name: Configure
       env:
         CC: ${{ matrix.CC }}