This CL is based on the patch:

chrome/nacl.gypi

 # Copyright (c) 2011 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.
 
 {
+  'includes': [
+    '../native_client/build/untrusted.gypi',
+  ],
   'target_defaults': {
     'variables': {
       'nacl_target': 0,
     },
     'target_conditions': [
       # This part is shared between the targets defined below. Only files and
       # settings relevant for building the Win64 target should be added here.
       ['nacl_target==1', {
         'include_dirs': [
           '<(INTERMEDIATE_DIR)',
@@ skipping 39 matching lines @@
     ],
   },
   'conditions': [
     ['disable_nacl!=1', {
       'targets': [
         {
           'target_name': 'nacl',
           'type': 'static_library',
           'variables': {
             'nacl_target': 1,
-            'irt_build_cmd': [
-              'python', 'build_nacl_irt.py', '--outdir', '<(PRODUCT_DIR)',
-            ],
-            'irt_inputs_cmd':
-                'python build_nacl_irt.py --inputs',
-          },
+           },
           'dependencies': [
+            # TODO(gregoryd): chrome_resources and chrome_strings could be
+            # shared with the 64-bit target, but it does not work due to a gyp
+            # issue
             'chrome_resources',
             'chrome_strings',
             'common',
+            '../ppapi/native_client/native_client.gyp:nacl_irt',
             '../webkit/support/webkit_support.gyp:glue',
             '../ppapi/native_client/src/trusted/plugin/plugin.gyp:ppGoogleNaClPluginChrome',
             '../native_client/src/trusted/service_runtime/service_runtime.gyp:sel',
             '../native_client/src/trusted/platform_qualify/platform_qualify.gyp:platform_qual_lib',
           ],
           'direct_dependent_settings': {
             'defines': [
               'NACL_BLOCK_SHIFT=5',
               'NACL_BLOCK_SIZE=32',
               '<@(nacl_defines)',
             ],
           },
-          'conditions': [
-            ['OS=="win"', {
-              # Windows needs both the x86-32 and x86-64 IRT.
-              'actions': [
-                {
-                  'action_name': 'nacl_irt',
-                  'message': 'Building NaCl IRT',
-                  'inputs': [
-                    '<!@(<(irt_inputs_cmd) --platform=x86-32 --platform=x86-64)',
-                  ],
-                  'outputs': ['<(PRODUCT_DIR)/nacl_irt_x86_32.nexe',
-                              '<(PRODUCT_DIR)/nacl_irt_x86_64.nexe'],
-                  'action': [
-                    '<@(irt_build_cmd)',
-                    '--platform', 'x86-32',
-                    '--platform', 'x86-64',
-                  ],
-                },
-              ],
-            }],
-            ['OS!="win" and target_arch=="ia32"', {
-              # Linux-x86-32 and OSX need only the x86-32 IRT.
-              'actions': [
-                {
-                  'action_name': 'nacl_irt',
-                  'message': 'Building NaCl IRT',
-                  'inputs': [
-                    '<!@(<(irt_inputs_cmd) --platform=x86-32)',
-                  ],
-                  'outputs': ['<(PRODUCT_DIR)/nacl_irt_x86_32.nexe'],
-                  'action': [
-                    '<@(irt_build_cmd)', '--platform', 'x86-32',
-                  ],
-                },
-              ],
-            }],
-            ['OS!="win" and target_arch=="x64"', {
-              # Linux-x86-64 needs only the x86-64 IRT.
-              'actions': [
-                {
-                  'action_name': 'nacl_irt',
-                  'message': 'Building NaCl IRT',
-                  'inputs': [
-                    '<!@(<(irt_inputs_cmd) --platform=x86-64)',
-                  ],
-                  'outputs': ['<(PRODUCT_DIR)/nacl_irt_x86_64.nexe'],
-                  'action': [
-                    '<@(irt_build_cmd)', '--platform', 'x86-64',
-                  ],
-                },
-              ],
-            }],
-            ['OS!="win" and target_arch=="arm"', {
-              'actions': [
-                {
-                  'action_name': 'nacl_irt',
-                  'message': 'Building NaCl IRT',
-                  'inputs': [
-                    '<!@(<(irt_inputs_cmd) --platform=arm)',
-                  ],
-                  'outputs': ['<(PRODUCT_DIR)/nacl_irt_arm.nexe'],
-                  'action': [
-                    '<@(irt_build_cmd)', '--platform', 'arm',
-                  ],
-                },
-              ],
-            }],
-          ],
         },
       ],
       'conditions': [
         ['OS=="win"', {
           'targets': [
             {
               'target_name': 'nacl_win64',
               'type': 'static_library',
               'variables': {
                 'nacl_target': 1,
@@ skipping 240 matching lines @@
               'target_name': 'nacl_win64',
               'type': 'none',
               'sources': [],
             },
           ],
         }],
       ],
     }],
   ],
 }