.github: add free-disk-space action to generic x86_64 workflow

Addresses disk space issues in GitHub Actions for generic x86_64 builds
by removing unused tools (Android SDK, .NET, Docker images, etc.) before
the build starts.  This frees up ~30GB of space.

Fixes #1210

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

.github/workflows/generic-x86-build.yml

@@ -10,6 +10,17 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: Free Disk Space
+        uses: jlumbroso/free-disk-space@main
+        with:
+          tool-cache: true
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: true
+          docker-images: true
+          swap-storage: false
+
       - name: Install build dependencies
         run: |
           sudo apt-get update