Update build.yaml

Author: cloudwebrtc

.github/workflows/build.yaml

@@ -110,6 +110,8 @@ jobs:
           channel: 'stable'
       - name: Install project dependencies
         run: flutter pub get
+      - name: Run apt update
+        run: sudo apt-get update
       - name: Install ninja-build libgtk-3-dev
         run: sudo apt-get install -y ninja-build libgtk-3-dev
       - name: Start Linux Build