Remove broken work-around for specifying build platforms for the operator image

Author: rooftopcellist

testdata/memcached-molecule-operator/Makefile

@@ -45,14 +45,11 @@ docker-push: ## Push docker image with the manager.
 # 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: test ## 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: ## 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 ${IMG} -f Dockerfile.cross .
+	- docker buildx build --push --platform=$(PLATFORMS) --tag ${IMG} -f Dockerfile .
 	- docker buildx rm project-v3-builder
-	rm Dockerfile.cross
 
 ##@ Deployment