compiles. Based loosely on mkdep.old.compiler (so CSRG license copied),
but now uses just one rewrite (awk) process per cpp invocation and
determines the proper way to run cpp and awk via a "configure" script.
Use HOST_MKDEP in bsd.hostlib/hostprog.mk (defaulting to the old override
value of MKDEP), and give it a TOOLDIR equivalent in bsd.own.mk.