Set host_arch to ia32 on machines with a 32bit userland but a 64bit kernel.

build/standalone.gypi

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 33 matching lines @@
     'variables': {
       'variables': {
         'variables': {
           'conditions': [
             ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or \
                OS=="netbsd" or OS=="mac" or OS=="qnx"', {
               # This handles the Unix platforms we generally deal with.
               # Anything else gets passed through, which probably won't work
               # very well; such hosts should pass an explicit target_arch
               # to gyp.
-              'host_arch%':
-                '<!(uname -m | sed -e "s/i.86/ia32/;\
-                                       s/x86_64/x64/;\
-                                       s/amd64/x64/;\
-                                       s/arm.*/arm/;\
-                                       s/aarch64/arm64/;\
-                                       s/mips.*/mipsel/")',
+              'host_arch%': '<!pymod_do_main(detect_v8_host_arch)',
             }, {
               # OS!="linux" and OS!="freebsd" and OS!="openbsd" and
               # OS!="netbsd" and OS!="mac"
               'host_arch%': 'ia32',
             }],
           ],
         },
         'host_arch%': '<(host_arch)',
         'target_arch%': '<(host_arch)',
       },
@@ skipping 286 matching lines @@
         ],
         'target_conditions': [
           ['_type!="static_library"', {
             'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-search_paths_first']},
           }],
         ],  # target_conditions
       },  # target_defaults
     }],  # OS=="mac"
   ],
 }