ci: add workflow to build and push release multi-arch Docker images

Rather than letting Dockerhub build the images (which only suppports
building amd64 in the subscription the Cilium project is using), use a
GitHub actions workflow to build and push Docker images for amd64 and
arm64 on release.

Signed-off-by: Tobias Klauser <[email protected]>

Author: tklauser

.github/workflows/images.yaml

@@ -0,0 +1,48 @@
+name: Image Release Build
+
+on:
+  pull_request: {}
+  push:
+    tags:
+      - 'v*'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.event.after }}
+  cancel-in-progress: true
+
+jobs:
+  build-and-push-prs:
+    if: ${{ github.repository == 'cilium/pwru' }}
+    environment: ${{ github.ref_type == 'tag' && 'release' }}
+    runs-on: ubuntu-24.04
+
+    steps:
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@18ce135bb5112fa8ce4ed6c17ab05699d7f3a5e0 # v3.11.0
+
+      - name: Login to DockerHub
+        uses: docker/login-action@74a5d142397b4f367a81961eba4e8cd7edddf772 # v3.4.0
+        with:
+          username: ${{ secrets.DOCKER_HUB_RELEASE_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_RELEASE_PASSWORD }}
+
+      - name: Getting image tag
+        id: tag
+        run: |
+          tag=${GITHUB_REF##*/}
+          echo tag=$tag >> $GITHUB_OUTPUT
+          echo image_tags=${{ github.repository_owner }}/pwru:$tag,quay.io/${{ env.QUAY_ORGANIZATION }}/${{ matrix.name }}:$tag >> $GITHUB_OUTPUT
+
+      - name: Checkout Source Code
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          ref: ${{ steps.tag.outputs.tag }}
+
+      - name: Docker Build
+        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
+        with:
+          context: .
+          file: ./Dockerfile
+          platforms: linux/arm64,linux/amd64
+          push: ${{ github.event_name == 'push' }}
+          tags: ${{ steps.tag.outputs.image_tags }}