buildroot

patch: add upstream security fix

Fixes CVE-2018-1000156: arbitrary command execution in ed-style patches.

Depend on MMU for now, because the patch adds a fork() call. Upstream
later switched to gnulib provided execute(), so this dependency can be
dropped on the next version bump.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>