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)
