Provide a default definition of the target_arch variable on Linux to...

build/common_global.gypi

 # Copyright (c) 2009 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.
 
 # This file contains flags that are specific to o3d, but affect the build as a
 # whole (e.g. build flags that change the ABI).
 # For example, on linux amd64, all the libraries that will be linked into the
 # plugin (skia, v8, ...) need to be compiled with -fPIC but we don't want to do
 # that generally in Chrome (so it can't be lumped into the top-level
 # build/common.gypi).
 {
   'variables': {
     'conditions': [
       [ 'OS == "linux"', {
         'use_system_zlib': 0,
         'use_system_libjpeg': 0,
+        'nacl_standalone': 1,
+        # nacl_standalone=1 is broken because nacl's build/common.gypi
+        # insists on building 32-bit. Force target_arch to be defined
+        # so that nacl's override isn't used.
+        # Note: this variable setting is copied from nacl's
+        # build/common.gypi so that it has the exact same semantics.
+        'target_arch%': '<!(uname -m | sed -e "s/i.86/ia32/;s/x86_64/x64/;s/arm.*/arm/")'
       }],
       [ 'OS == "win"', {
         'nacl_standalone': 1,
       }],
     ],
   },
   'target_defaults': {
     'conditions': [
       [ 'OS == "linux" and target_arch=="x64"', {
         'cflags': [
@@ skipping 15 matching lines @@
             'GCC_ENABLE_CPP_EXCEPTIONS': 'YES',
             'OTHER_CFLAGS': ['-mmacosx-version-min=10.5'],
           },
           'defines': [
             'MAC_OS_X_VERSION_MIN_REQUIRED=MAC_OS_X_VERSION_10_5',
           ],
       }],
     ],
   },
 }