lorder: Clean up and improve robustness.

lorder: Clean up and improve robustness.

* Properly parse (no) command-line options.

* Ensure that errors go to stderr and result in a non-zero exit.

* Drop the special-case code for a single argument, as it will produce
  the wrong outcome if the file does not exist or is corrupted.

* Don't print anything until after we've collected all the data.

* Always create all temporary files before setting the trap.  This
  ensures that the trap can safely fire at any moment, regardless of any
  previous definition of `T`.

* Use a temporary file rather than a pipe between `nm` and `sed` to
  ensure proper termination if `nm` fails due to a missing or invalid
  input.

* The check for self-referential entries was conditional on testing our
  argument list against a regex looking for archives.  This was a
  needless and unreliable optimization; make the check unconditional.

* Document that lorder will not work properly if any of its inputs have
  spaces in their name.

MFC after:	1 week
Sponsored by:	Klara, Inc.
Reviewed by:	allanjude
Differential Revision:	https://reviews.freebsd.org/D44133