FYI: I've committed more table-driven changes to to bsd.own.mk in -current:
   OBJECT_FMT	set to either "a.out" or "ELF".
   NOSHLIB	set on powerpc, unset elswhere

and changed four Makefiles where tests on MACHINE or MACHINE_ARCH were
actually probing for the object format. I've tested these on i386 and
on a pmax, and (for ld.elf_so) on a pmax pretending to be an Alpha,
and the right things happened.

There may be problems on PowerPC. bsd.lib.mk has had rules to build
shared-lib .so files on a PowerPC since the first round of
`table-driven' Makefile changes.  That's probably a bug, but I haven't
changed it (yet).  As usual, if you find any problems, send a PR.

And some advance warning: if you haven't rebuilt ld, do sow now!

This change don't depend on the new commandline features of a.out ld;
I'll be committing bsd.lib.mk changes for that tomorrow, and removing
all differences between how we create and install shared libraries
between ELF and a.out ports. (This is for the benefit of packages that
build, or use, shared libraries.)  So, rebuild ld if you havent already.