Remove hack in __gthread_active_p() to always return 0 on x86_64

gcc/gthr-nacl.h

 /* Threads compatibility routines for libgcc2 and libobjc.  */
 /* Compile this one with gcc.  */
 /* Copyright (C) 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
    Free Software Foundation, Inc.
 
 This file is part of GCC.
 
 GCC is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free
 Software Foundation; either version 2, or (at your option) any later
@@ skipping 98 matching lines @@
 
 static inline int
 __gthread_active_p (void)
 {
   /*
    * The threading library is active if a basic thread creation/destruction
    * primitive is referenced.  Unfortunately we don't have those yet.
    * TODO: change to reference a thread creation/destruction function
    *             when one becomes available.
    */
-  // This is a dirty workaround over our inability to use locks in NaCl x86-64.
-  // TODO(pasko): fix this by enabling correct builtins.
-#ifndef __x86_64__
   static void *const __gthread_active_ptr
     = __extension__ (void *) &__gthrw_(pthread_mutex_lock);
   return __gthread_active_ptr != 0;
-#else
-  return 0;
-#endif
 }
 
 #ifdef _LIBOBJC
 
 /* This is the config.h file in libobjc/ */
 #include <config.h>
 
 #ifdef HAVE_SCHED_H
 # include <sched.h>
 #endif
@@ skipping 412 matching lines @@
 
 static inline int
 __gthread_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex)
 {
   return __gthread_mutex_unlock (mutex);
 }
 
 #endif /* _LIBOBJC */
 
 #endif /* ! GCC_GTHR_POSIX_H */