Use custom sources for GH Actions build on Ubuntu

.github/workflows/build_linux.yml

@@ -11,7 +11,7 @@ jobs:
     - name: Install dependencies
       run: |
         sudo rm -f /etc/apt/sources.list.d/*
-        sudo cp -f .github/workflows/build_linux_sources.list /etc/apt/sources.list
+        sudo cp -f Development/Scripts/Linux/build_linux_sources.list /etc/apt/sources.list
         sudo apt-get update
         sudo apt-get install libx11-dev libxcursor-dev libxinerama-dev build-essential gettext libtool libtool-bin libpulse-dev libasound2-dev libjack-dev portaudio19-dev
     - name: Checkout repo