Merge pull request #740 from Daimler/fix-makefile-goproxy

🐛  Pass GOPROXY environment variable to Docker image build

Author: k8s-ci-robot

Makefile

@@ -202,7 +202,7 @@ generate-manifests: $(CONTROLLER_GEN) ## Generate manifests e.g. CRD, RBAC etc.
 
 .PHONY: docker-build
 docker-build: ## Build the docker image for controller-manager
-	docker build --pull --build-arg ARCH=$(ARCH) --build-arg LDFLAGS="$(LDFLAGS)" . -t $(CONTROLLER_IMG)-$(ARCH):$(TAG)
+	docker build --pull --build-arg goproxy=$(GOPROXY) --build-arg ARCH=$(ARCH) --build-arg LDFLAGS="$(LDFLAGS)" . -t $(CONTROLLER_IMG)-$(ARCH):$(TAG)
 	MANIFEST_IMG=$(CONTROLLER_IMG)-$(ARCH) MANIFEST_TAG=$(TAG) $(MAKE) set-manifest-image
 	$(MAKE) set-manifest-pull-policy