Add multi-arch image builds to makefile

A default set of platforms is specified and will build those if var `PLATFORMS` is not specified on the CLI

Issue ansible#31 fixes ansible#1680

Author: jon-nfc

Makefile

@@ -107,6 +107,21 @@ docker-build: ## Build docker image with the manager.
 docker-push: ## Push docker image with the manager.
 	${CONTAINER_CMD} push ${IMG}
 
+# PLATFORMS defines the target platforms for  the manager image be build to provide support to multiple
+# architectures. (i.e. make docker-buildx IMG=myregistry/mypoperator:0.0.1). To use this option you need to:
+# - able to use docker buildx . More info: https://docs.docker.com/build/buildx/
+# - have enable BuildKit, More info: https://docs.docker.com/develop/develop-images/build_enhancements/
+# - be able to push the image for your registry (i.e. if you do not inform a valid value via IMG=<myregistry/image:<tag>> than the export will fail)
+# To properly provided solutions that supports more than one platform you should use this option.
+PLATFORMS ?= linux/arm64,linux/amd64,linux/s390x,linux/ppc64le
+.PHONY: docker-buildx
+docker-buildx: ## Build and push docker image for the manager for cross-platform support
+	- docker buildx create --name project-v3-builder
+	docker buildx use project-v3-builder
+	- docker buildx build --push --platform=$(PLATFORMS) --tag ${IMG} -f Dockerfile .
+	- docker buildx rm project-v3-builder
+
+
 ##@ Deployment
 
 .PHONY: install