Allow build-time selection between ia32 and x86_64 in the GYP/Xcode Mac Chromium build

src/mips/assembler-mips.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 16 matching lines @@
 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // The original source code covered by the above license above has been
 // modified significantly by Google Inc.
 // Copyright 2010 the V8 project authors. All rights reserved.
 
 
 #include "v8.h"
+
+#if defined(V8_TARGET_ARCH_MIPS)
+
 #include "mips/assembler-mips-inl.h"
 #include "serialize.h"
 
 
 namespace v8 {
 namespace internal {
 
 
 
 const Register no_reg = { -1 };
@@ skipping 1152 matching lines @@
     *p = LUI | rt_code | ((itarget & HIMask)>>16);
     *(p+1) = ORI | rt_code | (rt_code << 5) | (itarget & LOMask);
   }
 
   CPU::FlushICache(pc, 2 * sizeof(int32_t));
 }
 
 
 } }  // namespace v8::internal
 
+#endif  // V8_TARGET_ARCH_MIPS