Fix GitHub workflow not installing packages properly

Author: Blixibon

.github/workflows/mapbase_build-base.yml

@@ -194,7 +194,9 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Install GCC/G++ multilib
-      run: sudo apt-get install gcc-multilib g++-multilib
+      run: |
+        sudo apt-get update
+        sudo apt-get install gcc-multilib g++-multilib
 
     - name: Pick game
       if: inputs.project-group == 'game' || inputs.project-group == 'shaders'