cmd/compile: use internal/race

CL 14870 added internal/race to factor out duplicated race thunks,
we should use it.

No signification changes in compile time and compile binary size.

Change-Id: I786af44dd5bb0f4ab6709432eeb603f27a5b6c63
Reviewed-on: https://go-review.googlesource.com/c/go/+/178118
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/norace.go

@@ -1,9 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build !race
-
-package gc
-
-const raceEnabled = false

src/cmd/compile/internal/gc/pgen.go

@@ -13,6 +13,7 @@ import (
 	"cmd/internal/src"
 	"cmd/internal/sys"
 	"fmt"
+	"internal/race"
 	"math/rand"
 	"sort"
 	"sync"
@@ -325,7 +326,7 @@ func compileSSA(fn *Node, worker int) {
 }
 
 func init() {
-	if raceEnabled {
+	if race.Enabled {
 		rand.Seed(time.Now().UnixNano())
 	}
 }
@@ -336,7 +337,7 @@ func init() {
 func compileFunctions() {
 	if len(compilequeue) != 0 {
 		sizeCalculationDisabled = true // not safe to calculate sizes concurrently
-		if raceEnabled {
+		if race.Enabled {
 			// Randomize compilation order to try to shake out races.
 			tmp := make([]*Node, len(compilequeue))
 			perm := rand.Perm(len(compilequeue))

src/cmd/compile/internal/gc/race.go

@@ -1,9 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build race
-
-package gc
-
-const raceEnabled = true

src/cmd/dist/buildtool.go

@@ -90,6 +90,7 @@ var bootstrapDirs = []string{
 	"debug/macho",
 	"debug/pe",
 	"internal/goversion",
+	"internal/race",
 	"internal/xcoff",
 	"math/big",
 	"math/bits",