NaCl SDK: Have hello world example to check for __pnacl__ instead of __CLANG__.

native_client_sdk/src/examples/hello_world/hello_world.c

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /** @file hello_world.c
  * This example demonstrates loading, running and scripting a very simple
  * NaCl module.
  */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/c/pp_module.h"
 #include "ppapi/c/pp_var.h"
 #include "ppapi/c/ppb.h"
 #include "ppapi/c/ppb_console.h"
 #include "ppapi/c/ppb_instance.h"
 #include "ppapi/c/ppb_messaging.h"
 #include "ppapi/c/ppb_var.h"
 #include "ppapi/c/ppp.h"
 #include "ppapi/c/ppp_instance.h"
 #include "ppapi/c/ppp_messaging.h"
 
 #if defined(__native_client__)
-#if defined(__CLANG__)
+#if defined(__pnacl__)
 #define TCNAME "pnacl"
 #elif defined(__GLIBC__)
 #define TCNAME "glibc"
 #else
 #define TCNAME "newlib"
 #endif
 #else
 #define TCNAME "host"
 #endif
 
@@ skipping 173 matching lines @@
   }
   return NULL;
 }
 
 
 /**
  * Called before the plugin module is unloaded.
  */
 PP_EXPORT void PPP_ShutdownModule() {
 }