I've just committed changes to bsd.lib.mk to start using the new
features in our a.out ld -- the GNU-binutils-compatible commandline
syntax for building dynamically-linked shared objects, or .so files.
These will show up in tomorrow's sup.

If you are tracking current on an a.out system, please be sure to
build and install the new ld before using tomorrow's sup.

I've verified this builds a functional libc.so on i386, but as usual,
send a PR if there are any problems.

I'll be committing another change, to build ELF-style symlinks
to .so files at both build and install time, in a day or so.