configure: Fix sem_timedwait probe

(cherry-picked from libav commit 41262498)
Signed-off-by: James Almer <jamrial@gmail.com>

configure

@@ -5750,7 +5750,6 @@ check_builtin atomic_cas_ptr atomic.h "void **ptr; void *oldval, *newval; atomic
 check_builtin machine_rw_barrier mbarrier.h "__machine_rw_barrier()"
 check_builtin MemoryBarrier windows.h "MemoryBarrier()"
 check_builtin sarestart signal.h "SA_RESTART"
-check_builtin sem_timedwait semaphore.h "sem_t *s; sem_init(s,0,0); sem_timedwait(s,0); sem_destroy(s)" -lpthread
 check_builtin sync_val_compare_and_swap "" "int *ptr; int oldval, newval; __sync_val_compare_and_swap(ptr, oldval, newval)"
 check_builtin gmtime_r time.h "time_t *time; struct tm *tm; gmtime_r(time, tm)"
 check_builtin localtime_r time.h "time_t *time; struct tm *tm; localtime_r(time, tm)"
@@ -5935,7 +5934,7 @@ if enabled pthreads; then
 fi
 
 enabled pthreads &&
-    check_builtin sem_timedwait semaphore.h "sem_t *s; sem_init(s,0,0); sem_timedwait(s,0); sem_destroy(s)"
+    check_builtin sem_timedwait semaphore.h "sem_t *s; sem_init(s,0,0); sem_timedwait(s,0); sem_destroy(s)" $pthreads_extralibs
 
 enabled  zlib && check_lib zlib   zlib.h      zlibVersion    -lz
 enabled bzlib && check_lib bzlib bzlib.h BZ2_bzlibVersion    -lbz2