Remove not used variable from POSIX thread code

src/thread_posix.c

@@ -4,14 +4,13 @@
 
 static void *bh_thread_run(void *arg)
 {
-    bh_tls_t *tls;
     bh_task_t *task;
 
     /* Fetch thread data */
     task = (bh_task_t *)arg;
 
     /* Setup TLS */
-    tls = bh_tls_fetch();
+    bh_tls_fetch();
 
     /* Do the task, mark as done, and if required free it */
     task->func(task->data);