mk/cc.mk: make implicit function declarations fatal (#136)
mk/cc.mk: make implicit function declarations fatal (#136)

Avoids issues with missing prototypes causing truncation of pointers.

Signed-off-by: Sergei Trofimovich <110fdadc76b6bce16977f568bdb4723eaed6fb3f@gentoo.org>
dwfreed/openrc,williamh/openrc,OpenRC/openrc,dwfreed/openrc,williamh/openrc,williamh/openrc,dwfreed/openrc,OpenRC/openrc,OpenRC/openrc