Enable x64 build for Android

build/android.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 166 matching lines @@
               ['target_arch=="mipsel"', {
                 'ldflags': [
                   '-L<(android_stlport_libs)/mips',
                 ],
               }],
               ['target_arch=="ia32"', {
                 'ldflags': [
                   '-L<(android_stlport_libs)/x86',
                 ],
               }],
+              ['target_arch=="x64"', {
+                'ldflags': [
+                  '-L<(android_stlport_libs)/x86_64',
+                ],
+              }],
               ['target_arch=="arm64"', {
                 'ldflags': [
                   '-L<(android_stlport_libs)/arm64',
                 ],
               }],
             ],
           }],
           ['target_arch=="ia32"', {
             # The x86 toolchain currently has problems with stack-protector.
             'cflags!': [
@@ skipping 48 matching lines @@
           ['_type=="static_library"', {
             'ldflags': [
               # Don't export symbols from statically linked libraries.
               '-Wl,--exclude-libs=ALL',
             ],
           }],
         ],
       }],  # _toolset=="target"
       # Settings for building host targets using the system toolchain.
       ['_toolset=="host"', {
-        'cflags': [ '-m32', '-pthread' ],
-        'ldflags': [ '-m32', '-pthread' ],
+        'conditions': [
+          ['target_arch=="x64"', {
+            'cflags': [ '-m64', '-pthread' ],
+            'ldflags': [ '-m64', '-pthread' ],
+          }, {
+            'cflags': [ '-m32', '-pthread' ],
+            'ldflags': [ '-m32', '-pthread' ],
+          }],
+        ],
         'ldflags!': [
           '-Wl,-z,noexecstack',
           '-Wl,--gc-sections',
           '-Wl,-O1',
           '-Wl,--as-needed',
         ],
       }],
     ],  # target_conditions
   },  # target_defaults
 }