runtime: use correct traceback file on arm reported by fred richter
runtime: use correct traceback file on arm
reported by fred richter

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/5494062
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go