Enable Multi-Arch Container Image Builds

Previous to this change official descheduler container images only
supported the AMD64 hardware architecture. This change enables
building official descheduler container images for multiple
architectures.

The initially supported architectures are AMD64 and ARM64.

Dockerfile

@@ -15,8 +15,9 @@ FROM golang:1.15.2
 
 WORKDIR /go/src/sigs.k8s.io/descheduler
 COPY . .
+ARG ARCH
 ARG VERSION
-RUN VERSION=${VERSION} make
+RUN VERSION=${VERSION} make build.$ARCH
 
 FROM scratch
 

Makefile

@@ -18,6 +18,7 @@
 VERSION?=v$(shell date +%Y%m%d)-$(shell git describe --tags --match "v*")
 BUILD=$(shell date +%FT%T%z)
 LDFLAG_LOCATION=sigs.k8s.io/descheduler/cmd/descheduler/app
+ARCHS = amd64 arm64
 
 LDFLAGS=-ldflags "-X ${LDFLAG_LOCATION}.version=${VERSION} -X ${LDFLAG_LOCATION}.buildDate=${BUILD}"
 
@@ -47,18 +48,40 @@ all: build
 build:
 	CGO_ENABLED=0 go build ${LDFLAGS} -o _output/bin/descheduler sigs.k8s.io/descheduler/cmd/descheduler
 
+build.amd64:
+	CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build ${LDFLAGS} -o _output/bin/descheduler sigs.k8s.io/descheduler/cmd/descheduler
+
+build.arm64:
+	CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build ${LDFLAGS} -o _output/bin/descheduler sigs.k8s.io/descheduler/cmd/descheduler
+
 dev-image: build
 	docker build -f Dockerfile.dev -t $(IMAGE) .
 
 image:
-	docker build --build-arg VERSION="$(VERSION)" -t $(IMAGE) .
+	docker build --build-arg VERSION="$(VERSION)" --build-arg ARCH="amd64" -t $(IMAGE) .
 
-push-container-to-gcloud: image
+image.amd64:
+	docker build --build-arg VERSION="$(VERSION)" --build-arg ARCH="amd64" -t $(IMAGE)-amd64 .
+
+image.arm64:
+	docker build --build-arg VERSION="$(VERSION)" --build-arg ARCH="arm64" -t $(IMAGE)-arm64 .
+
+push: image
 	gcloud auth configure-docker
 	docker tag $(IMAGE) $(IMAGE_GCLOUD)
 	docker push $(IMAGE_GCLOUD)
 
-push: push-container-to-gcloud
+push-all: image.amd64 image.arm64
+	gcloud auth configure-docker
+	for arch in $(ARCHS); do \
+		docker tag $(IMAGE)-$${arch} $(IMAGE_GCLOUD)-$${arch} ;\
+		docker push $(IMAGE_GCLOUD)-$${arch} ;\
+	done
+	DOCKER_CLI_EXPERIMENTAL=enabled docker manifest create $(IMAGE_GCLOUD) $(addprefix --amend $(IMAGE_GCLOUD)-, $(ARCHS))
+	for arch in $(ARCHS); do \
+		DOCKER_CLI_EXPERIMENTAL=enabled docker manifest annotate --arch $${arch} $(IMAGE_GCLOUD) $(IMAGE_GCLOUD)-$${arch} ;\
+	done
+	DOCKER_CLI_EXPERIMENTAL=enabled docker manifest push $(IMAGE_GCLOUD) ;\
 
 clean:
 	rm -rf _output

cloudbuild.yaml

@@ -14,7 +14,7 @@ steps:
     - VERSION=$_GIT_TAG
     - BASE_REF=$_PULL_BASE_REF
     args:
-    - push
+    - push-all
 substitutions:
   # _GIT_TAG will be filled with a git-based tag for the image, of the form vYYYYMMDD-hash, and
   # can be used as a substitution