race.bash: support freebsd
race.bash: support freebsd

R=golang-codereviews, iant
CC=golang-codereviews
https://codereview.appspot.com/110150044

tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go