Fix arm simulator build on Max OS X. For some reason the GCC version...

src/arm/virtual-frame-arm.cc

 // Copyright 2009 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 489 matching lines @@
       break;
     case R0_R1_TOS:
       masm()->push(r1);
       // Fall through.
     case R0_TOS:
       masm()->push(r0);
       top_of_stack_state_ = NO_TOS_REGISTERS;
       // Fall through.
     case NO_TOS_REGISTERS:
       break;
+    default:
+      UNREACHABLE();
+      break;
   }
   ASSERT(register_allocation_map_ == 0);  // Not yet implemented.
 }
 
 #undef __
 
 } }  // namespace v8::internal