build: use repository-local GOBIN for less finicky builds

This commit adjusts our Makefile to set GOBIN to $(REPO_ROOT)/bin before
embarking upon a build. This has two benefits:

    1. Previously, users who had set GOBIN to something other than the
       default $GOPATH/bin would have a broken build. We'd extend the
       PATH to include $GOPATH/bin, but `go install` would put binaries
       in $GOBIN, and later build steps would be unable to find the
       built tools. By forcing GOBIN to a known value in the Makefile,
       users can no longer break the build by having a non-default GOBIN
       set in their environment.

    2. Since Go has a single global namespace for installed binaries
       (i.e., the GOBIN directory), if the user had installed a
       different version of one of our dependencies, or a different tool
       with a binary of the same name, we'd blow away that binary during
       our install process. Even worse, later re-installs of the other
       tool could blow away the version we installed without our build
       process noticing. Using a repository-local GOBIN solves this.

Fixes cockroachdb#6886.

.gitignore

@@ -12,6 +12,7 @@
 #   git config --global core.excludesfile ~/.gitignore_global)
 
 artifacts
+/bin
 .bootstrap
 .buildinfo
 /cockroach

Makefile

@@ -112,13 +112,14 @@ install: override LINKFLAGS += \
 	-X "github.com/cockroachdb/cockroach/pkg/build.utcTime=$(shell date -u '+%Y/%m/%d %H:%M:%S')" \
 	-X "github.com/cockroachdb/cockroach/pkg/build.rev=$(shell cat .buildinfo/rev)"
 
+# Special case: we install the cockroach binary to the user-specified GOBIN
+# (usually GOPATH/bin) rather than our repository-local GOBIN.
+install: GOBIN := $(ORIGINAL_GOBIN)
 # Note: We pass `-v` to `go build` and `go test -i` so that warnings
 # from the linker aren't suppressed. The usage of `-v` also shows when
 # dependencies are rebuilt which is useful when switching between
 # normal and race test builds.
 install: .buildinfo/tag .buildinfo/rev
-	@echo "GOPATH set to $$GOPATH"
-	@echo "$$GOPATH/bin added to PATH"
 	$(GO) $(BUILDMODE) -v $(GOFLAGS) -tags '$(TAGS)' -ldflags '$(LINKFLAGS)' $(BUILDTARGET)
 
 # Build, but do not run the tests.

build/common.mk

@@ -37,6 +37,19 @@ export GOPATH := $(realpath $(ORG_ROOT)/../../..)
 #                                       |  |~ GOPATH/src
 #                                       |~ GOPATH/src/github.com
 
+# Avoid printing twice if Make restarts (because a Makefile was changed) or is
+# called recursively from another Makefile.
+ifeq ($(MAKE_RESTARTS)$(MAKELEVEL),0)
+$(info GOPATH set to $(GOPATH))
+endif
+
+# We install our vendored tools to a directory within this repository to avoid
+# overwriting any user-installed binaries of the same name in the default GOBIN.
+# We must remember the original value of GOBIN so we can install the cockroach
+# binary to the user's GOBIN instead of our repository-local GOBIN.
+ORIGINAL_GOBIN := $(GOBIN)
+export GOBIN := $(abspath $(REPO_ROOT)/bin)
+
 # Prefer tools we've installed with go install and Yarn to those elsewhere on
 # the PATH.
 #
@@ -46,7 +59,7 @@ export GOPATH := $(realpath $(ORG_ROOT)/../../..)
 # ORG_ROOT. It's much simpler to add the Yarn executable-installation directory
 # to the PATH than have protobuf.mk adjust its paths to work in both ORG_ROOT
 # and UI_ROOT.
-export PATH := $(GOPATH)/bin:$(UI_ROOT)/node_modules/.bin:$(PATH)
+export PATH := $(GOBIN):$(UI_ROOT)/node_modules/.bin:$(PATH)
 
 # HACK: Make has a fast path and a slow path for command execution,
 # but the fast path uses the PATH variable from when make was started,

build/protobuf.mk

@@ -27,9 +27,9 @@ GOGO_PROTOBUF_TYPES_PACKAGE := $(GOGO_PROTOBUF_PACKAGE)/types
 GOGO_PROTOBUF_PATH := $(GITHUB_ROOT)/../$(GOGO_PROTOBUF_PACKAGE)
 PROTOBUF_PATH  := $(GOGO_PROTOBUF_PATH)/protobuf
 
-PROTOC          := $(GOPATH)/bin/protoc
+PROTOC          := $(GOBIN)/protoc
 PLUGIN_SUFFIX   := gogoroach
-PROTOC_PLUGIN   := $(GOPATH)/bin/protoc-gen-$(PLUGIN_SUFFIX)
+PROTOC_PLUGIN   := $(GOBIN)/protoc-gen-$(PLUGIN_SUFFIX)
 GOGOPROTO_PROTO := $(GOGO_PROTOBUF_PATH)/gogoproto/gogo.proto
 
 COREOS_PATH := $(GITHUB_ROOT)/coreos

build/variables.mk

@@ -17,13 +17,15 @@ define VALID_VARS
   GITHOOKSDIR
   GIT_DIR
   GO
+  GOBIN
   GOFLAGS
   GOPATH
   GORACE
   GOVERS
   LINKFLAGS
   MACOSX_DEPLOYMENT_TARGET
   ORG_ROOT
+  ORIGINAL_GOBIN
   PATH
   PKG
   PKG_ROOT