meson: Add missing thread_dep to atomic-test
Otherwise it won't link.
/usr/bin/ld: /tmp/atomic-test.uzrv5D.ltrans0.ltrans.o:
undefined reference to symbol 'pthread_setaffinity_np@@GLIBC_2.3.4'
Otherwise it won't link.
/usr/bin/ld: /tmp/atomic-test.uzrv5D.ltrans0.ltrans.o:
undefined reference to symbol 'pthread_setaffinity_np@@GLIBC_2.3.4'