[tlbuild] build of new dvisvgm fails

[Martin Gieseking]

> In short, current source works on rocky9 (karl at home). (I'll double check.)
> Fails on alma8 (tug).
> Fails on centos7 (gh).
> 
> Presumably something changed in how dvisvgm-3.2 (vs. earlier versions)
> does its dl stuff, since that's why it would be failing now.
> 
> Unfortunately I won't be able to track this down today.
> 
> Martin, if you have any ideas about where to look along these lines,
> that would be great :). --thanks, karl.

Hi Karl and Norbert,

unfortunately, I can't really tell what's going wrong here yet. 
configure checks for dlopen and should add -ldl if necessary. The log 
from the failed build at GitHub contains these lines:

2024-01-18T00:11:48.0075957Z configure: not linking to libgs, trying to 
arrange for dynamic loading
2024-01-18T00:11:48.0078312Z checking for library containing dlopen... 
(cached) -ldl

As configure detects -ldl, the flag should be added to LIBS but for some 
reason LIBS gets overwritten or is not passed to the linking stage. It 
works with non-TL builds, though. Therefore, there's probably an issue 
somewhere in an adapted autoconf or automake script.

Best regards
Martin