runtime/race: add Windows support

This is copy of https://golang.org/cl/6810080
but sent from another account (dvyukov@gmail.com is not in CONTRIBUTORS).

R=rsc
CC=golang-dev
https://golang.org/cl/6827060

src/cmd/go/build.go

@@ -1840,8 +1840,8 @@ func raceInit() {
 	if !buildRace {
 		return
 	}
-	if goarch != "amd64" || goos != "linux" && goos != "darwin" {
-		fmt.Fprintf(os.Stderr, "go %s: -race is only supported on linux/amd64 and darwin/amd64\n", flag.Args()[0])
+	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])
 		os.Exit(2)
 	}
 	buildGcflags = append(buildGcflags, "-b")

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
+// +build race,linux,amd64 race,darwin,amd64 race,windows,amd64
 
 // Package race provides low-level facilities for data race detection.
 package race

src/run.bat

@@ -52,6 +52,15 @@ go test sync -short -timeout=120s -cpu=10
 if errorlevel 1 goto fail
 echo.
 
+if not "%GOHOSTOS%-%GOOS%-%GOARCH%-%CGO_ENABLED%" == "windows-windows-amd64-1" goto norace
+echo # Testing race detector.
+go test -race -i flag
+if errorlevel 1 goto fail
+go test -race -short flag
+if errorlevel 1 goto fail
+echo.
+:norace
+
 echo # ..\misc\dashboard\builder ..\misc\goplay
 go build ..\misc\dashboard\builder ..\misc\goplay
 if errorlevel 1 goto fail