XXX: Make we somehow more descriptive

Building a FreeBSD kernel i386 called file:DEBUG on an amd64 can cause some headache: build# sh -c 'MACHINE_ARCH=i386 MACHINE=i386 MAKEOBJDIRPREFIX=/usr/obj/nanobsd.wleiden/i386 make KERNCONF=DEBUG NO_MODULES=yes buildkernel'

Then install kernel CF is mounted at file:/mnt : # sh -c 'MACHINE_ARCH=i386 MACHINE=i386 MAKEOBJDIRPREFIX=/usr/obj/nanobsd.wleiden/i386 make KERNCONF=DEBUG NO_MODULES=yes installkernel PREFIX=/mnt'