Log Message:
lang/gcc5: add patch to avoid declaring a prototype of host_detect_local_cpu
on platforms which do not include driver-arm.o in gcc/config.host, and do
not have this function. such as netbsd/arm.

an alternative would be to add driver-arm.o for the netbsd/arm case too, but
it would be diverging from netbsd base gcc, and /proc/cpuinfo which is needed
for this function to do anything useful is empty at least on my machine.

(I still can't complete a build on ARM)