Fix code location when mounting to docker-cli-shell-validate

Signed-off-by: Jean-Pierre Huynh <jean-pierre.huynh@ounet.fr>

docker.Makefile

@@ -87,4 +87,4 @@ yamldocs: build_docker_image
 
 .PHONY: shellcheck
 shellcheck: build_shell_validate_image
-	docker run -ti --rm -v "$(CURDIR)":/tmp $(VALIDATE_IMAGE_NAME) make shellcheck
+	docker run -ti --rm $(MOUNTS) $(VALIDATE_IMAGE_NAME) make shellcheck

dockerfiles/Dockerfile.shellcheck

@@ -4,6 +4,6 @@ RUN apt-get update && \
     apt-get -y install make shellcheck && \
     apt-get clean
 
-WORKDIR /tmp
+WORKDIR /go/src/github.com/docker/cli
 
 CMD bash