[FAB-9288] default gotools to $GOPATH/bin

Restores assumptions about GOPATH being set during build and pointing to
s single location.

Explicit tools target can be set by using the GOTOOLS_BINDIR variable at
build time.

make gotools GOTOOLS_BINDIR=$HOME/bin

Change-Id: Id71b512d475cc23c12a501db94af25fff4c65a38
Signed-off-by: Matthew Sykes <sykesmat@us.ibm.com>

Author: sykesm

gotools.mk

@@ -6,7 +6,7 @@
 GOTOOLS = dep golint goimports protoc-gen-go ginkgo gocov gocov-xml misspell
 BUILD_DIR ?= .build
 GOTOOLS_GOPATH ?= $(BUILD_DIR)/gotools
-GOTOOLS_BINDIR ?= $(GOTOOLS_GOPATH)/bin
+GOTOOLS_BINDIR ?= $(GOPATH)/bin
 
 # go tool->path mapping
 go.fqp.golint    := github.com/golang/lint/golint