Non-SFI mode: Use clone() instead of pthread_create()

src/untrusted/pthread/nc_thread.c

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /*
  * Native Client threads library
  */
 
@@ skipping 254 matching lines @@
   ANNOTATE_NOT_HAPPENS_BEFORE_MUTEX(&__nc_thread_management_lock);
 
   if (pthread_cond_init(&__nc_last_thread_cond, NULL) != 0)
     __builtin_trap();
   STAILQ_INIT(&__nc_thread_memory_blocks[0]);
   STAILQ_INIT(&__nc_thread_memory_blocks[1]);
 
   __nc_thread_initialized = 1;
 }
 
-#if defined(NACL_IN_IRT)
-
 /*
  * This is used by the IRT for user threads.  We initialize all fields
  * so that we get predictable behaviour in case some IRT code does an
  * unsupported pthread operation on a user thread.
  */
 void __nc_initialize_unjoinable_thread(struct nc_combined_tdb *tdb) {
   nc_tdb_init(&tdb->tdb, &tdb->basic_data);
   tdb->tdb.joinable = 0;
 }
 
-#else
+#if !defined(NACL_IN_IRT)
 
 /*
  * Will be called from the library startup code,
  * which always happens on the application's main thread.
  */
 void __pthread_initialize(void) {
   __pthread_initialize_minimal(TDB_SIZE);
 
   struct nc_combined_tdb *tdb = (struct nc_combined_tdb *) __nc_get_tdb();
   nc_tdb_init(&tdb->tdb, &tdb->basic_data);
@@ skipping 512 matching lines @@
 
 /*
  * We include this directly in this file rather than compiling it
  * separately because there is some code (e.g. libstdc++) that uses weak
  * references to all pthread functions, but conditionalizes its calls only
  * on one symbol.  So if these functions are in another file in a library
  * archive, they might not be linked in by static linking.
  */
 /* @IGNORE_LINES_FOR_CODE_HYGIENE[1] */
 #include "native_client/src/untrusted/pthread/nc_tsd.c"