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

src/platform-linux.cc

 // Copyright 2012 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 277 matching lines @@
   }
   fclose(f);
 
   // Did not find string in the proc file.
   return false;
 }
 #endif  // def __mips__
 
 
 int OS::ActivationFrameAlignment() {
-#ifdef V8_TARGET_ARCH_ARM
+#if V8_TARGET_ARCH_ARM
   // On EABI ARM targets this is required for fp correctness in the
   // runtime system.
   return 8;
 #elif V8_TARGET_ARCH_MIPS
   return 8;
 #endif
   // With gcc 4.4 the tree vectorization optimizer can generate code
   // that requires 16 byte alignment such as movdqa on x86.
   return 16;
 }
@@ skipping 678 matching lines @@
   limit_mutex = CreateMutex();
 }
 
 
 void OS::TearDown() {
   delete limit_mutex;
 }
 
 
 } }  // namespace v8::internal