busybox

diff: return 1 when skipping directories with -r, but without -N

Diff in diffutils will return 1 in case -r option is specified without
-N something exists only in one of the directories.

Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>