improve Makefile

Makefile

@@ -1,11 +1,35 @@
+# Copyright 2019 The Kubernetes Authors.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#     http://www.apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+DBG_MAKEFILE ?=
+ifeq ($(DBG_MAKEFILE),1)
+    $(warning ***** starting Makefile for goal(s) "$(MAKECMDGOALS)")
+    $(warning ***** $(shell date))
+else
+    # If we're not debugging the Makefile, don't echo recipes.
+    MAKEFLAGS += -s
+endif
+
+.PHONY: generate
 generate:
 	GO111MODULE=on go generate
 
+.PHONY: run
 run:
 	GO111MODULE=on go run .
 
+.PHONY: build
 build:
 	GO111MODULE=on go build .
 
+.PHONY: check
 check:
 	GO111MODULE=on ./scripts/check-everything.sh