debug/gosym: in test, use temp binary name in /tmp, and clean up.
debug/gosym: in test, use temp binary name in /tmp, and clean up.

This fixes all.bash on shared machines.

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/5992078
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go