Add NO_OBJ to those directories that don't make anything.

Add NO_OBJ to those directories that don't make anything.

For directories that don't many anything, add NO_OBJ=t just before we
include bsd.init.mk. This prevents them from creating an OBJ
directory. In addition, prevent defs.mk from creating the machine
related links in these cases. They aren't needed and break, at least
on stable, the read-only src tree build.