third_party: Link uid_wrapper against pthread

third_party: Link uid_wrapper against pthread

uid_wrapper uses pthread_atfork() which is only provided by libpthread.                                                                                   │····················
So we need an explicit dependency.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14140

Signed-off-by: Andreas Schneider <asn@samba.org>
Signed-off-by: Isaac Boukris <iboukris@gmail.com>
Pair-Programmed-With: Isaac Boukris <iboukris@gmail.com>
Reviewed-by: Matthias Dieter Wallnöfer <mdw@samba.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>
(cherry picked from commit bd0cd8e13234d684da77a65f6fdaea2572625369)