Clean up the usage of V8_TARGET_ARCH_${arch} and V8_HOST_ARCH_${arch}

test/cctest/test-macro-assembler-x64.cc

 // Copyright 2009 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 1113 matching lines @@
   masm->GetCode(&desc);
   // Call the function from C++.
   int result = FUNCTION_CAST<F0>(buffer)();
   CHECK_EQ(0, result);
 }
 
 
 void TestSmiDiv(MacroAssembler* masm, Label* exit, int id, int x, int y) {
   bool division_by_zero = (y == 0);
   bool negative_zero = (x == 0 && y < 0);
-#ifdef V8_TARGET_ARCH_X64
+#if V8_TARGET_ARCH_X64
   bool overflow = (x == Smi::kMinValue && y < 0);  // Safe approx. used.
 #else
   bool overflow = (x == Smi::kMinValue && y == -1);
 #endif
   bool fraction = !division_by_zero && !overflow && (x % y != 0);
   __ Move(r11, Smi::FromInt(x));
   __ Move(r14, Smi::FromInt(y));
   if (!fraction && !overflow && !negative_zero && !division_by_zero) {
     // Division succeeds
     __ movq(rcx, r11);
@@ skipping 1368 matching lines @@
   CodeDesc desc;
   masm->GetCode(&desc);
   // Call the function from C++.
   int result = FUNCTION_CAST<F0>(buffer)();
   CHECK_EQ(0, result);
 }
 
 
 
 #undef __