On Linux, "mktemp tmp-XXXX" will not work. Also, redirect stderr on which,
so it does not complain too loudly. After all, this test should only be
executed when old binaries are available.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Junio C Hamano <junkio@cox.net>