[tlbuild] build of new dvisvgm fails

[Bruno Haible]

Karl Berry wrote:
> glibc package has libdl.so etc. But also the dlsym/etc. symbols are
> usually defined in glibc itself.
> ...
> In short, current source works on rocky9 (karl at home). (I'll double check.)
> Fails on alma8 (tug).
> Fails on centos7 (gh).

Up until glibc 2.33, dlopen, dlsym, etc. existed only in libdl, i.e.
the linker option '-ldl' was required.

Starting with glibc 2.34, they are also available from libc, i.e.
'-ldl' is no longer required. [1]

Bruno

[1] https://sourceware.org/pipermail/libc-alpha/2021-August/129718.html