Add "mtls_descriptor=desc" to preconfigure.ac and regenerate preconfigure.
Fix failure: elf/tst-gnu2-tls2.
Reported-by: Joseph S. Myers <josmyers@redhat.com> Reported-by: Andreas K. Huettel <dilfridge@gentoo.org>
(cherry picked from commit d4cdb601df0a125550341f85d7011314e4746308)