PNaCl: Build a PPAPI shims library for all architectures

ppapi/native_client/src/untrusted/pnacl_irt_shim/shim_entry.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/include/elf32.h"
 #include "native_client/src/include/elf_auxv.h"
 #include "native_client/src/include/nacl_macros.h"
 #include "native_client/src/untrusted/pnacl_irt_shim/shim_ppapi.h"
 #include "native_client/src/untrusted/nacl/nacl_startup.h"
 
 
 /*
  * This is the true entry point for untrusted code.
  * See nacl_startup.h for the layout at the argument pointer.
  */
 void _pnacl_wrapper_start(uint32_t *info) {
+  /* The PNaCl PPAPI shims are only needed on x86-64. */
+#if defined(__x86_64__)
   Elf32_auxv_t *auxv = nacl_startup_auxv(info);
 
   Elf32_auxv_t *entry = NULL;
   for (Elf32_auxv_t *av = auxv; av->a_type != AT_NULL; ++av) {
     if (av->a_type == AT_SYSINFO) {
       entry = av;
       break;
     }
   }
 
@@ skipping 12 matching lines @@
 
   /* If entry is NULL still allow startup to continue.  It may be the case
    * that the IRT was not actually used (e.g., for some commandline tests).
    * For newlib, we can tell that the IRT isn't used when libnacl_sys_private.a
    * is in the bitcode link line. However, glibc does not use
    * libnacl_sys_private, so that would not work. We could look for -lppapi
    * in the bitcode link line, but looking at the bitcode link line
    * seems brittle (what if the bitcode link was separated from translation).
    * Thus we always wrap _start, even if there is no IRT auxv entry.
    */
+#endif
 
   /*
    * Call the user entry point function.  It should not return.
    * TODO(sehr): Find a way to ensure this is invoked via a tail call.
    */
   _start(info);
 }