Makefile: improve tooling

This commit improves the tooling for the repo and makes all go binaries
managed with go mod. This ensures all tooling is vendored.

tools.go

@@ -0,0 +1,26 @@
+// Copyright 2019 the Kilo 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.
+
+// +build tools
+
+package main
+
+import (
+	_ "golang.org/x/lint/golint"
+	_ "k8s.io/code-generator/cmd/client-gen"
+	_ "k8s.io/code-generator/cmd/deepcopy-gen"
+	_ "k8s.io/code-generator/cmd/informer-gen"
+	_ "k8s.io/code-generator/cmd/lister-gen"
+	_ "k8s.io/kube-openapi/cmd/openapi-gen"
+)