build: Build multi-arch (linux/amd64, linux/arm64) image using buildx

.github/workflows/release.yaml

@@ -17,6 +17,7 @@ jobs:
   release:
     name: Release
     runs-on:
+      # For a list of pre-installed software, see https://github.com/actions/runner-images/blob/main/images/linux/Ubuntu2204-Readme.md
       - ubuntu-22.04
     steps:
       - uses: actions/checkout@v3
@@ -31,29 +32,22 @@ jobs:
           registry: ${{ env.registry }}
           username: ${{ env.registry_username }}
           password: ${{ env.registry_password }}
-      - name: Generate container image
+      - name: Build multi-arch container image, and push to container registry
         # Note: We set make variables using positional arguments (to the right of the make command), not environment
         # variables (to the left of the make command). While make converts environment variables to make variables, the
         # conversion is not straightforward. For example, conditional assignments are not overriden by environment
         # variables.
-        run: |
-          make generate-capvcd-image \
-            REGISTRY=${{ env.registry }} \
-            CAPVCD_IMG=${{ env.repository }} \
-            VERSION=${{ env.version }}
-      - name: Push container image to container registry
-        # See note on make variables, above.
         run: |
           make push-capvcd-image \
+            --makefile d2iq.Makefile \
             REGISTRY=${{ env.registry }} \
             CAPVCD_IMG=${{ env.repository }} \
             VERSION=${{ env.version }}
       - name: Generate GitHub release artifacts
         # See note on make variables, above.
-        #
-        # We use our own Makefile to allow us to change the image in the manifest.
         run: |
-          make -f d2iq.Makefile release-manifests \
+          make release-manifests \
+            --makefile d2iq.Makefile
             REGISTRY=${{ env.registry }} \
             CAPVCD_IMG=${{ env.repository }} \
             VERSION=${{ env.version }}

d2iq.Makefile

@@ -1,5 +1,25 @@
 include Makefile
 
+PLATFORMS := "linux/amd64,linux/arm64"
+
+# The multi-platform build must push its output to a registry, because the Docker Engine image store does not support
+# multi-platform images.  This will be addressed when Docker Engine supports the containerd image store. See
+# https://docs.docker.com/storage/containerd.
+.PHONY: push-capvcd-image
+push-capvcd-image: docker-buildx-builder generate fmt vet vendor
+	docker buildx build \
+		--builder capvcd \
+		--platform $(PLATFORMS) \
+		--output=type=registry \
+		--build-arg VERSION=$(VERSION) \
+		--tag $(REGISTRY)/$(CAPVCD_IMG):$(VERSION) \
+		--file Dockerfile \
+		.
+
+.PHONY: docker-buildx-builder
+docker-buildx-builder:
+	docker buildx inspect --bootstrap capvcd &>/dev/null || docker buildx create --name capvcd
+
 # The upstream 'release-manifests' target does not correctly override the image.
 # We work around this by using `kustomize edit set image`.
 release-manifests: kustomize