Cross-compile zookeeper operator for amd64 and arm64. (#30)

* Cross-compile zookeeper operator for amd64 and arm64.

* Implement review

Makefile

@@ -23,6 +23,7 @@ GIT_SHA=$(shell git rev-parse --short HEAD)
 TEST_IMAGE=$(TEST_REPO)-testimages:$(VERSION)
 DOCKER_TEST_PASS=testzkop@123
 DOCKER_TEST_USER=testzkop
+IMG?=$(REPO):$(VERSION)
 .PHONY: all build check clean test
 # Get the currently used golang install path (in GOPATH/bin, unless GOBIN is set)
 ifeq (,$(shell go env GOBIN))
@@ -133,6 +134,23 @@ build-image:
 	docker build --build-arg VERSION=$(VERSION) --build-arg DOCKER_REGISTRY=$(DOCKER_REGISTRY) --build-arg DISTROLESS_DOCKER_REGISTRY=$(DISTROLESS_DOCKER_REGISTRY) --build-arg GIT_SHA=$(GIT_SHA) -t $(REPO):$(VERSION) .
 	docker tag $(REPO):$(VERSION) $(REPO):latest
 
+# PLATFORMS defines the target platforms for the manager image be built to provide support to multiple
+# architectures. (i.e. make docker-buildx IMG=myregistry/mypoperator:0.0.1). To use this option you need to:
+# - be able to use docker buildx. More info: https://docs.docker.com/build/buildx/
+# - have enabled BuildKit. More info: https://docs.docker.com/develop/develop-images/build_enhancements/
+# - be able to push the image to your registry (i.e. if you do not set a valid value via IMG=<myregistry/image:<tag>> then the export will fail)
+# To adequately provide solutions that are compatible with multiple platforms, you should consider using this option.
+PLATFORMS ?= linux/arm64,linux/amd64
+.PHONY: docker-buildx
+docker-buildx: ## Build and push docker image for the manager for cross-platform support
+	# copy existing Dockerfile and insert --platform=${BUILDPLATFORM} into Dockerfile.cross, and preserve the original Dockerfile
+	sed -e '1 s/\(^FROM\)/FROM --platform=\$$\{BUILDPLATFORM\}/; t' -e ' 1,// s//FROM --platform=\$$\{BUILDPLATFORM\}/' Dockerfile > Dockerfile.cross
+	- docker buildx create --name zookeeper-builder
+	docker buildx use zookeeper-builder
+	docker buildx build --push --platform=$(PLATFORMS) --tag $(IMG) -f Dockerfile.cross .
+	- docker buildx rm zookeeper-builder
+	rm Dockerfile.cross
+
 build-zk-image:
 
 	docker build --build-arg VERSION=$(VERSION)  --build-arg DOCKER_REGISTRY=$(DOCKER_REGISTRY) --build-arg GIT_SHA=$(GIT_SHA) -t $(APP_REPO):$(VERSION) ./docker