Make lint work without a $GOPATH. (#1374)

Also document the need for $GOBIN to be in developer's $PATH.

Signed-off-by: Marcin Owsiany <mowsiany@D2iQ.com>

CONTRIBUTING.md

@@ -34,7 +34,7 @@ You can find the full text of the DCO here: https://developercertificate.org/
 ### Pre-requisites
 
 - Git
-- Go `1.13` or later
+- Go `1.13` or later. Note that some [Makefile](Makefile) targets assume that your `$GOBIN` is in your `$PATH`.
 - [Kubebuilder](https://book.kubebuilder.io/quick-start.html#installation) version 2 or later - note that it is only needed for the `kube-apiserver` and `etcd` binaries, so no need to install *its* dependencies (such as `kustomize`).
 - A Kubernetes Cluster running version `1.13` or later (e.g., [kind](https://kind.sigs.k8s.io/) or [Minikube](https://kubernetes.io/docs/tasks/tools/install-minikube/))
 - [kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/)

Makefile

@@ -47,8 +47,10 @@ test-clean:
 
 .PHONY: lint
 lint:
-	if [ ! -f ${GOPATH}/bin/golangci-lint ]; then ./hack/install-golangcilint.sh; fi
-	${GOPATH}/bin/golangci-lint run
+ifeq (, $(shell which golangci-lint))
+	./hack/install-golangcilint.sh
+endif
+	golangci-lint run
 
 .PHONY: download
 download: