Update Makefile

Makefile

@@ -2,10 +2,10 @@
 include Makefile.env
 
 # Put it first so that "make" without argument is like "make help".
-build: docker-build
-release: docker-build docker-release
+build: docker-build build-date
+release: docker-build build-date docker-release
 
-.PHONY: docker-build docker-release
+.PHONY: docker-build build-date docker-release
 
 docker-build:
 	docker build --build-arg VERSION="${version}" \
@@ -16,3 +16,8 @@ docker-build:
 
 docker-release:
 	docker push ${CONTAINER_REGISTRY}/${CONTAINER_REPOSITORY}:${version}
+
+build-date:
+	# Ensures there is always an asset to upload
+	mkdir -p build
+	date > build/build-date