Add multiarch building support for arm64

Signed-off-by: Bin Lu <bin.lu@arm.com>

Makefile

@@ -4,6 +4,7 @@ DEV_IMAGE         ?= golang:1.11
 SHORT_NAME        ?= tiller
 SHORT_NAME_RUDDER ?= rudder
 TARGETS           ?= darwin/amd64 linux/amd64 linux/386 linux/arm linux/arm64 linux/ppc64le linux/s390x windows/amd64
+LINUX_ARCH        ?= amd64 386 arm arm64 ppc64le s390x
 DIST_DIRS         = find * -type d -exec
 
 # go option
@@ -69,6 +70,20 @@ docker-build: check-docker docker-binary
 	docker build --rm -t ${IMAGE} rootfs
 	docker tag ${IMAGE} ${MUTABLE_IMAGE}
 
+# Building multi-arch docker images
+.PHONY: docker-build-all
+docker-build-all: BINDIR = ./rootfs
+docker-build-all: check-docker build-cross
+docker-build-all:
+	docker run --rm --privileged multiarch/qemu-user-static:register --reset
+	for arch in $(LINUX_ARCH); do \
+			cp $(BINDIR)/Dockerfile ./_dist/linux-$$arch; \
+			docker build --platform=linux/$$arch -t ${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${SHORT_NAME}-$$arch:${DOCKER_VERSION} \
+				./_dist/linux-$$arch; \
+			docker tag ${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${SHORT_NAME}-$$arch:${DOCKER_VERSION} \
+				${DOCKER_REGISTRY}/${IMAGE_PREFIX}/${SHORT_NAME}-$$arch:${MUTABLE_VERSION}; \
+	done
+
 .PHONY: docker-binary-rudder
 docker-binary-rudder: BINDIR = ./rootfs
 docker-binary-rudder: GOFLAGS += -a -installsuffix cgo