CI: Cancel existing builds when PR branch is updated

Signed-off-by: Frank Osterfeld <[email protected]>

.github/workflows/ci.yml

@@ -61,6 +61,10 @@ jobs:
     name: "${{ matrix.compiler.cc }} | ${{ matrix.cmake-build-type }}"
     needs: buildAndPublishDocker
     runs-on: "ubuntu-latest"
+    concurrency:
+      # Cancel running builds inside work (PR) branches
+      group: ${{ github.head_ref }}
+      cancel-on-progress: ${{ github.ref != 'refs/heads/main' }}
     container:
       image: "${{ needs.buildAndPublishDocker.outputs.container }}"
     strategy: