Do not build prebuilts for kiev firmware branch

BUG=chrome-os-partner:8699
TEST=None yet

Change-Id: I12d1fae83d921da93b0c2597ebfc29c3af17778a
Reviewed-on: https://gerrit.chromium.org/gerrit/19681
Tested-by: Eric Blake <eblake@chromium.org>
Reviewed-by: Eric Blake <eblake@chromium.org>
1 file changed