Added up-get update to avoid issues when apt cache gets stale

Author: Ithyx

.github/workflows/linux.yml

@@ -11,6 +11,7 @@ jobs:
     - uses: actions/checkout@v1
     - name: install dependencies
       run: |
+        sudo apt-get update
         sudo apt-get install ninja-build -y
         sudo apt-get install xorg-dev
         sudo apt-get install freeglut3-dev