runtime/race: support freebsd

All tests pass except one test in regexp package.

LGTM=iant
R=golang-codereviews, iant, dave
CC=golang-codereviews
https://golang.org/cl/107270043

src/cmd/go/build.go

@@ -64,7 +64,7 @@ and test commands:
 		The default is the number of CPUs available.
 	-race
 		enable data race detection.
-		Supported only on linux/amd64, darwin/amd64 and windows/amd64.
+		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-v
 		print the names of packages as they are compiled.
 	-work
@@ -2556,8 +2556,8 @@ func raceInit() {
 	if !buildRace {
 		return
 	}
-	if goarch != "amd64" || goos != "linux" && goos != "darwin" && goos != "windows" {
-		fmt.Fprintf(os.Stderr, "go %s: -race is only supported on linux/amd64, darwin/amd64 and windows/amd64\n", flag.Args()[0])
+	if goarch != "amd64" || goos != "linux" && goos != "freebsd" && goos != "darwin" && goos != "windows" {
+		fmt.Fprintf(os.Stderr, "go %s: -race is only supported on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64\n", flag.Args()[0])
 		os.Exit(2)
 	}
 	buildGcflags = append(buildGcflags, "-race")

src/cmd/go/doc.go

@@ -82,7 +82,7 @@ and test commands:
 		The default is the number of CPUs available.
 	-race
 		enable data race detection.
-		Supported only on linux/amd64, darwin/amd64 and windows/amd64.
+		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-v
 		print the names of packages as they are compiled.
 	-work

src/pkg/runtime/race/race.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build race,linux,amd64 race,darwin,amd64 race,windows,amd64
+// +build race,linux,amd64 race,freebsd,amd64 race,darwin,amd64 race,windows,amd64
 
 package race