ci: Cleanup dockers

Author: hdiethelm

.github/workflows/docker.yml

@@ -52,4 +52,15 @@ jobs:
             BASE_IMAGE=debian:${{ matrix.debian_version }}
         push: true
         outputs: type=image,name=target,annotation-index.org.opencontainers.image.description=LinuxCNC build image
-        tags: ghcr.io/${{ github.repository_owner }}/linuxcnc/build-container:${{ matrix.debian_version }}-${{ matrix.runner_arch }}-latest
+        tags: ghcr.io/${{ github.repository_owner }}/linuxcnc/build-container:${{ matrix.debian_version }}-${{ matrix.runner_arch }}-latest
+
+  cleanup-docker:
+    runs-on: ubuntu-24.04
+    steps:
+    - name: Cleanup untagged images
+      uses: actions/delete-package-versions@v5
+      with:
+        package-name: 'build-container'
+        package-type: 'container'
+        min-versions-to-keep: 10
+        delete-only-untagged-versions: 'true'