Use docker buildx for etcd image

This allows to choose the correct architecture in the image manifest,
which defaulted to the host system before applying this patch.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

cluster/images/etcd/Makefile

@@ -34,7 +34,7 @@ LATEST_ETCD_VERSION?=3.5.0
 # REVISION provides a version number for this image and all it's bundled
 # artifacts. It should start at zero for each LATEST_ETCD_VERSION and increment
 # for each revision of this image at that etcd version.
-REVISION?=3
+REVISION?=4
 
 # IMAGE_TAG Uniquely identifies k8s.gcr.io/etcd docker image with a tag of the form "<etcd-version>-<revision>".
 IMAGE_TAG=$(LATEST_ETCD_VERSION)-$(REVISION)
@@ -84,6 +84,8 @@ endif
 
 RUNNERIMAGE?=gcr.io/distroless/static:latest
 
+QEMUVERSION?=5.2.0-2
+
 build:
 	# Explicitly copy files to the temp directory
 	$(BIN_INSTALL) migrate-if-needed.sh $(TEMP_DIR)
@@ -143,13 +145,20 @@ else
 	cd $(TEMP_DIR) && echo "ENV ETCD_UNSUPPORTED_ARCH=$(ARCH)" >> Dockerfile
 endif
 
+	docker run --rm --privileged multiarch/qemu-user-static:$(QEMUVERSION) --reset -p yes
+	docker buildx version
+	BUILDER=$(shell docker buildx create --use)
+
 	# And build the image
-	docker build \
+	docker buildx build \
 		--pull \
+		--load \
+		--platform linux/$(ARCH) \
 		-t $(REGISTRY)/etcd-$(ARCH):$(IMAGE_TAG) \
 		--build-arg BASEIMAGE=$(BASEIMAGE) \
 		--build-arg RUNNERIMAGE=$(RUNNERIMAGE) \
 		$(TEMP_DIR)
+	docker buildx rm $$BUILDER
 
 push: build
 	docker tag $(REGISTRY)/etcd-$(ARCH):$(IMAGE_TAG) $(MANIFEST_IMAGE)-$(ARCH):$(IMAGE_TAG)

cluster/images/etcd/cloudbuild.yaml

@@ -14,6 +14,7 @@ steps:
       - IMAGE=gcr.io/$PROJECT_ID/etcd
       - BUILD_IMAGE=debian-build
       - TMPDIR=/workspace
+      - HOME=/root  # for docker buildx
     args:
       - '-c'
       - |