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

src/arm/debug-arm.cc

 // Copyright 2006-2008 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
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 //       with the distribution.
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 //       from this software without specific prior written permission.
 //
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 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "v8.h"
 
+#if defined(V8_TARGET_ARCH_ARM)
+
 #include "codegen-inl.h"
 #include "debug.h"
 
 namespace v8 {
 namespace internal {
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
 bool BreakLocationIterator::IsDebugBreakAtReturn() {
   return Debug::IsDebugBreakAtReturn(rinfo());
 }
@@ skipping 190 matching lines @@
 
 void Debug::SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
                                    Handle<Code> code) {
   UNREACHABLE();
 }
 const int Debug::kFrameDropperFrameSize = -1;
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal
+
+#endif  // V8_TARGET_ARCH_ARM