runtime/race: add end-to-end test on windows

whatever "end-to-end" means here

R=golang-dev, dvyukov
CC=golang-dev
https://golang.org/cl/12898044

src/run.bat

@@ -54,7 +54,9 @@ echo.
 
 if not "%GOHOSTOS%-%GOOS%-%GOARCH%-%CGO_ENABLED%" == "windows-windows-amd64-1" goto norace
 echo # Testing race detector.
-go test -race -i flag
+go test -race -i runtime/race flag
+if errorlevel 1 goto fail
+go test -race -run=Output runtime/race
 if errorlevel 1 goto fail
 go test -race -short flag
 if errorlevel 1 goto fail