PNaCl: Build a PPAPI shims library for all architectures

ppapi/native_client/src/untrusted/pnacl_irt_shim/shim_ppapi.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.
  */
 
 #include "native_client/src/untrusted/pnacl_irt_shim/shim_ppapi.h"
 
 #include <string.h>
 #include "native_client/src/shared/ppapi_proxy/ppruntime.h"
 #include "native_client/src/untrusted/irt/irt.h"
 #include "native_client/src/untrusted/irt/irt_ppapi.h"
 #include "ppapi/generators/pnacl_shim.h"
 
+/* The PNaCl PPAPI shims are only needed on x86-64. */
+#if defined(__x86_64__)
+
 TYPE_nacl_irt_query __pnacl_real_irt_interface;
 
 /*
  * These remember the interface pointers the user registers by calling the
  * IRT entry point.
  */
 static struct PP_StartFunctions user_start_functions;
 
 static int32_t wrap_PPPInitializeModule(PP_Module module_id,
                                         PPB_GetInterface get_browser_intf) {
@@ skipping 68 matching lines @@
       real_irt_ppapi_hook.ppapi_register_thread_creator;
   /*
    * Copy the interface structure into the client.
    */
   if (sizeof ppapi_hook <= tablesize) {
     memcpy(table, &ppapi_hook, sizeof ppapi_hook);
     return sizeof ppapi_hook;
   }
   return 0;
 }
+
+#endif