[PATCH 2/4 REVIEW] libtool.m4: fix nm BSD flag detection

[Nick Alcock]

On 7 Jul 2021, Nick Clifton told this:

> Hi Nick,
>
>> Ping?
>
> Oops.

I sent a bunch of pings out at the same time, to a bunch of different
projects. You are the only person to respond, so thank you!

>>> 	PR libctf/27482
>>> 	* libtool.m4 (LT_PATH_NM): Try BSDization flags with a user-provided
>
> Changes to libtool need to be posted to the libtool project:
>
>   https://www.gnu.org/software/libtool/

I considered this, but there is *serious* divergence between the
libtool.m4 in our tree and upstream. Fixing this divergence looks to be
a fairly major project in and of itself :( the last real sync looked
like being all the way back in 2008.

> They have mailing lists for bug reports and patch submissions.
>
> Once the patch has been accepted there it can be backported to the gcc and
> gdb/binutils repositories...

AIUI, libtool has no maintainer currently, and the divergence is such
that the patch might need a near-complete rewrite anyway :( (there were
changes to this function upstream in 2012 and 2013, long after our last
sync.)

(However, I'm going to try in any case. I may have found a sucker, er, I
mean coworker willing to take this on.)