update makefile for multi-arch controller-v2 docker build

make-linux.mk

@@ -432,8 +432,8 @@ central-controller-docker: _buildx FORCE
 	@echo Image: registry.zerotier.com/zerotier-central/ztcentral-controller:${TIMESTAMP}
 
 centralv2-controller-docker: _buildx FORCE
-	docker buildx build --platform linux/amd64,linux/arm64 --no-cache -t us-central1-docker.pkg.dev/zerotier-421eb9/docker-images/ztcentral-controller:$(git rev-parse --short HEAD) -f ext/central-controller-docker/Dockerfile --build-arg git_branch=`git name-rev --name-only HEAD` . --push
-	@echo Image: us-central1-docker.pkg.dev/zerotier-421eb9/docker-images/ztcentral-controller:$(git rev-parse --short HEAD)
+	docker buildx build --platform linux/amd64,linux/arm64 --no-cache -t us-central1-docker.pkg.dev/zerotier-421eb9/docker-images/ztcentral-controller:$(shell git rev-parse --short HEAD) -f ext/central-controller-docker/Dockerfile --build-arg git_branch=`git name-rev --name-only HEAD` . --push
+	@echo Image: us-central1-docker.pkg.dev/zerotier-421eb9/docker-images/ztcentral-controller:$(shell git rev-parse --short HEAD)
 
 debug:	FORCE
 	make ZT_DEBUG=1 one