Also apt install X11 tools for testing.

.github/workflows/test.yml

@@ -17,7 +17,9 @@ jobs:
           cmake-version: '3.13.x'
           
       - name: Get Libraries
-        run: git submodule update --init --recursive
+        run: |
+          git submodule update --init --recursive
+          sudo apt install xorg-dev libglu1-mesa-dev
 
       - name: Build
         run: |