runtime/pprof: disable testing under race detector

until we decide what to do with issues 5659/5736.
Profiling with race detector is not very useful in general,
and now it makes race builders red.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10523043

src/pkg/runtime/pprof/pprof_test.go

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// See issue 5659.
+// +build !race
+
 package pprof_test
 
 import (