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

src/arm/assembler-thumb2.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 18 matching lines @@
 // 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_ARM) && defined(V8_ARM_VARIANT_THUMB)
+
 #include "arm/assembler-thumb2-inl.h"
 #include "serialize.h"
 
 namespace v8 {
 namespace internal {
 
 // Safe default is no features.
 unsigned CpuFeatures::supported_ = 0;
 unsigned CpuFeatures::enabled_ = 0;
 unsigned CpuFeatures::found_by_runtime_probing_ = 0;
@@ skipping 1820 matching lines @@
     bind(&after_pool);
   }
 
   // Since a constant pool was just emitted, move the check offset forward by
   // the standard interval.
   next_buffer_check_ = pc_offset() + kCheckConstInterval;
 }
 
 
 } }  // namespace v8::internal
+
+#endif  // V8_TARGET_ARCH_ARM && V8_ARM_VARIANT_THUMB