Fix a couple of docker target problems (#1545)

* Fix `make local-docker-image` after docker file rename

Should this target exist? Not sure. However, this target does exist,
is pulled in by the acceptance test target automatically, and it was
broken. So fix it.

What this target used to do differently from the default targets was
to tag the image with an internal name instead of a public one. Should
this distinction exist? Not sure. However, as both targets exist, I'll
restore the distinction, too.

* Fix which docker image needs to embed flux

Makefile

@@ -44,9 +44,10 @@ local-kind-cluster-with-registry:
 local-registry:
 	./tools/deploy-local-registry.sh
 
-local-docker-image:
-	DOCKER_BUILDKIT=1 docker build -t localhost:5001/wego-app:latest . --build-arg FLUX_VERSION=$(FLUX_VERSION)
-	docker push localhost:5001/wego-app:latest
+local-docker-image: DOCKERFILE:=gitops-server.dockerfile
+local-docker-image: DOCKERARGS:=--build-arg FLUX_VERSION=$(FLUX_VERSION)
+local-docker-image: DOCKER_REGISTRY:=localhost:5001
+local-docker-image: _docker
 
 test: dependencies
 	go test -v ./core/...
@@ -77,7 +78,7 @@ endif
 gitops: bin/gitops ## Build the Gitops CLI, accepts a 'DEBUG' flag
 gitops-server: cmd/gitops-server/cmd/dist/index.html bin/gitops-server ## Build the Gitops UI server, accepts a 'DEBUG' flag
 
-DOCKER_REGISTRY?=localhost:5001
+DOCKER_REGISTRY?=ghcr.io/weaveworks/wego-app
 
 _docker:
 	DOCKER_BUILDKIT=1 docker build $(DOCKERARGS)\
@@ -86,10 +87,10 @@ _docker:
 										.
 
 docker-gitops: DOCKERFILE:=gitops.dockerfile
+docker-gitops: DOCKERARGS:=--build-arg FLUX_VERSION=$(FLUX_VERSION)
 docker-gitops: _docker ## Build a Docker image of the gitops CLI
 
 docker-gitops-server: DOCKERFILE:=gitops-server.dockerfile
-docker-gitops-server: DOCKERARGS:=--build-arg FLUX_VERSION=$(FLUX_VERSION)
 docker-gitops-server: _docker ## Build a Docker image of the Gitops UI Server
 
 # Clean up images and binaries