Add x64 to the gyp build.

tools/gyp/v8.gyp

Index: tools/gyp/v8.gyp
diff --git a/tools/gyp/v8.gyp b/tools/gyp/v8.gyp
index fc49620a14ab6441d574c2a9a3fceb881a421b2c..c8a2e85daa40e9fba31361ca2d36cb1272516fe1 100644
--- a/tools/gyp/v8.gyp
+++ b/tools/gyp/v8.gyp
@@ -52,6 +52,11 @@
           'V8_NATIVE_REGEXP',
         ],
       }],
+      ['target_arch=="x64"', {
+        'defines': [
+          'V8_TARGET_ARCH_X64',
+        ],
+      }],
     ],
     'configurations': {
       'Debug': {
@@ -428,6 +433,34 @@
             '../../src/ia32/virtual-frame-ia32.h',
           ],
         }],
+        ['target_arch=="x64"', {
+          'include_dirs+': [
+            '../../src/x64',
+          ],
+          'sources': [
+            '../../src/x64/assembler-x64-inl.h',
+            '../../src/x64/assembler-x64.cc',
+            '../../src/x64/assembler-x64.h',
+            '../../src/x64/builtins-x64.cc',
+            '../../src/x64/codegen-x64.cc',
+            '../../src/x64/codegen-x64.h',
+            '../../src/x64/cpu-x64.cc',
+            '../../src/x64/debug-x64.cc',
+            '../../src/x64/disasm-x64.cc',
+            '../../src/x64/frames-x64.cc',
+            '../../src/x64/frames-x64.h',
+            '../../src/x64/ic-x64.cc',
+            '../../src/x64/jump-target-x64.cc',
+            '../../src/x64/macro-assembler-x64.cc',
+            '../../src/x64/macro-assembler-x64.h',
+            #'../../src/x64/regexp-macro-assembler-x64.cc',
+            #'../../src/x64/regexp-macro-assembler-x64.h',
+            '../../src/x64/register-allocator-x64.cc',
+            '../../src/x64/stub-cache-x64.cc',
+            '../../src/x64/virtual-frame-x64.cc',
+            '../../src/x64/virtual-frame-x64.h',
+          ],
+        }],
         ['OS=="linux"', {
             'link_settings': {
               'libraries': [