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

src/execution.h

 // Copyright 2011 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 235 matching lines @@
   inline void set_interrupt_limits(const ExecutionAccess& lock);
 
   // Reset limits to actual values. For example after handling interrupt.
   // You should hold the ExecutionAccess lock when calling this method.
   inline void reset_limits(const ExecutionAccess& lock);
 
   // Enable or disable interrupts.
   void EnableInterrupts();
   void DisableInterrupts();
 
-#ifdef V8_TARGET_ARCH_X64
+#if V8_TARGET_ARCH_X64
   static const uintptr_t kInterruptLimit = V8_UINT64_C(0xfffffffffffffffe);
   static const uintptr_t kIllegalLimit = V8_UINT64_C(0xfffffffffffffff8);
 #else
   static const uintptr_t kInterruptLimit = 0xfffffffe;
   static const uintptr_t kIllegalLimit = 0xfffffff8;
 #endif
 
   class ThreadLocal {
    public:
     ThreadLocal() { Clear(); }
@@ skipping 32 matching lines @@
   friend class StackLimitCheck;
   friend class PostponeInterruptsScope;
 
   DISALLOW_COPY_AND_ASSIGN(StackGuard);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_EXECUTION_H_