Before deleting .git, determine the version and save it in .version file.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Message-id: 1395277315-7806-1-git-send-email-afaerber@suse.de
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>