meson: Build third_party/threads with hidden symbols

Fixes: acf13330 ("Initial meson build system")
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
5 jobs for meson-threads-symbols-hidden in 1 minute and 9 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Container
passed container #7799694

00:00:12

 
  Build
passed cmake #7799696

00:00:20

passed meson #7799698

00:00:35

failed meson #7799695

00:00:20

failed meson #7799697

00:00:19