all.bat: report error code back to the gobuilder
all.bat: report error code back to the gobuilder

not sure that it will work, but.

R=golang-dev, bradfitz
CC=golang-dev
http://codereview.appspot.com/5649051
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go