Makefile: fix permissions of mergetools/ checked out with permissive umask

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Junio C Hamano committed Oct 9, 2011 at 12:59 UTC 16f5bfcf65b46260f3a4fc66769e8b5cfd18a11a

No changes.