Create build structure for X64.

src/macro-assembler.h

Index: src/macro-assembler.h
diff --git a/src/macro-assembler.h b/src/macro-assembler.h
index d21f4796026c778057a34f629c4ea6d373b42770..2d93dac841225ddce816afed6d53d48399f8f4d1 100644
--- a/src/macro-assembler.h
+++ b/src/macro-assembler.h
@@ -28,23 +28,29 @@
 #ifndef V8_MACRO_ASSEMBLER_H_
 #define V8_MACRO_ASSEMBLER_H_
 
-#ifdef ARM
-
+#ifdef V8_ARCH_ARM
 #include "arm/constants-arm.h"
 #include "assembler.h"
 #include "arm/assembler-arm.h"
 #include "arm/assembler-arm-inl.h"
 #include "code.h"  // must be after assembler_*.h
 #include "arm/macro-assembler-arm.h"
+#endif
 
-#else  // ia32
+#ifdef V8_ARCH_X64
+#include "assembler.h"
+#include "x64/assembler-x64.h"
+#include "x64/assembler-x64-inl.h"
+#include "code.h"  // must be after assembler_*.h
+#include "x64/macro-assembler-x64.h"
+#endif
 
+#ifdef V8_ARCH_IA32
 #include "assembler.h"
 #include "ia32/assembler-ia32.h"
 #include "ia32/assembler-ia32-inl.h"
 #include "code.h"  // must be after assembler_*.h
 #include "ia32/macro-assembler-ia32.h"
-
 #endif
 
 #endif  // V8_MACRO_ASSEMBLER_H_