src: add race.bash
src: add race.bash

Add race.bash so anyone with suitable hardware can run a race detector build. race.bash can be called from the dashboard builder by passing -cmd="race.bash".

Original source for race.bash is here, http://code.google.com/p/go-wiki/wiki/DashboardBuilders

TODO: add race.bat for windows/amd64

R=dvyukov, minux.ma, adg, rsc
CC=fullung, golang-dev
https://codereview.appspot.com/7179052

apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,apparentlymart/golang,apparentlymart/golang,dsriram/golang,dsriram/golang,apparentlymart/golang,pombredanne/go-deleteme,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,apparentlymart/golang,dsriram/golang,dsriram/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,dsriram/golang,tv42/old-go,tv42/old-go,tv42/old-go,apparentlymart/golang,gnanderson/go,tv42/old-go,gnanderson/go,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,pombredanne/go-deleteme,dsriram/golang,tv42/old-go,gnanderson/go,tv42/old-go,apparentlymart/golang