ARM64: Fix ASM_LOCATION and the like.

BUG=
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/308023007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21620 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/checks.h

@@ -8,6 +8,7 @@
 #include <string.h>
 
 #include "../include/v8stdint.h"
+#include "base/build_config.h"
 
 extern "C" void V8_Fatal(const char* file, int line, const char* format, ...);
 
@@ -30,7 +31,8 @@ extern "C" void V8_Fatal(const char* file, int line, const char* format, ...);
 #endif
 
 // Simulator specific helpers.
-#if defined(USE_SIMULATOR) && defined(V8_TARGET_ARCH_ARM64)
+// We can't use USE_SIMULATOR here because it isn't defined yet.
+#if V8_TARGET_ARCH_ARM64 && !V8_HOST_ARCH_ARM64
   // TODO(all): If possible automatically prepend an indicator like
   // UNIMPLEMENTED or LOCATION.
   #define ASM_UNIMPLEMENTED(message)                                         \