Enable Native Client build of V8.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index a3c9ed0943bb9cac601e3ee3e43f43c04e2cd6fa..784d8b16849b5626fcbff02879002f53c8b2c6b8 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -35,6 +35,13 @@
     'CXX%': '${CXX:-$(which g++)}',  # Used to assemble a shell command.
     'v8_compress_startup_data%': 'off',
     'v8_target_arch%': '<(target_arch)',
+    # Native Client builds currently use the V8 ARM JIT and
+    # arm/simulator-arm.cc to defer the significant effort required
+    # for NaCl JIT support. The nacl_target_arch variable provides
+    # the 'true' target arch for places in this file that need it.
+    # TODO(bradchen): get rid of nacl_target_arch when someday
+    # NaCl V8 builds stop using the ARM simulator
+    'nacl_target_arch%': 'none',     # must be set externally
 
     # Setting 'v8_can_use_unaligned_accesses' to 'true' will allow the code
     # generated by V8 to do unaligned memory access, and setting it to 'false'
@@ -320,7 +327,8 @@
               'clang%': 0,
             },
             'conditions': [
-              ['OS!="android" or clang==1', {
+              ['(OS!="android" or clang==1) and \
+                nacl_target_arch!="nacl_x64"', {
                 'cflags': [ '<(m32flag)' ],
                 'ldflags': [ '<(m32flag)' ],
               }],