Fix the xcode build by not including x64 specific code when generating...

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 6298)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -25,6 +25,10 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#include "v8.h"
+
+#if defined(V8_TARGET_ARCH_X64)
+
 #include "x64/lithium-x64.h"
 #include "x64/lithium-codegen-x64.h"
 
@@ -1314,3 +1318,5 @@
 }
 
 } }  // namespace v8::internal
+
+#endif  // V8_TARGET_ARCH_X64