docker: additionally push arm64 compatible images

Author: davidmhewitt

.github/workflows/docker.yml

@@ -44,18 +44,27 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: arm64
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Build & push the base image to local registry
         uses: docker/[email protected]
         with:
           context: .
-          push: true
-          tags: localhost:5000/ubuntu-base:latest
+          load: true
+          platforms: linux/amd64,linux/arm64
+          tags: ubuntu-base:latest
 
       - name: Write the Dockerfile for the ${{ matrix.version }}-${{ matrix.arch }} runtime
         run: |
           cat <<EOF > ${{ matrix.version }}-${{ matrix.arch }}.Dockerfile
             # syntax = docker/dockerfile:experimental
-            FROM localhost:5000/ubuntu-base:latest
+            FROM ubuntu-base:latest
             RUN flatpak install -y --noninteractive appcenter io.elementary.Platform/${{ matrix.arch }}/${{ matrix.version }} io.elementary.Sdk/${{ matrix.arch }}/${{ matrix.version }}
           EOF
 
@@ -69,5 +78,6 @@ jobs:
         with:
           context: .
           push: true
+          platforms: linux/amd64,linux/arm64
           file: ${{ matrix.version }}-${{ matrix.arch }}.Dockerfile
           tags: ghcr.io/${{ github.repository }}/runtime:${{ matrix.version }}-${{ matrix.arch }}${{ env.additional_tags }}