getrevision.sh: Make sure we don't get translated output.

(And explicitly require bash.)

Signed-Off-By: Joerg Mayer <jmayer@loplof.de>
Acked-by: Stefan Tauner <stefan.tauner@student.tuwien.ac.at>

git-svn-id: svn://flashrom.org/flashrom/trunk@1716 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1