Fix product build on Linux clang.

runtime/vm/code_generator.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 689 matching lines @@
     Exceptions::PropagateError(Error::Cast(result));
   }
 }
 
 
 // Gets called from debug stub when code reaches a breakpoint
 // set on a runtime stub call.
 DEFINE_RUNTIME_ENTRY(BreakpointRuntimeHandler, 0) {
   if (!FLAG_support_debugger) {
     UNREACHABLE();
+    return;
   }
   DartFrameIterator iterator;
   StackFrame* caller_frame = iterator.NextFrame();
   ASSERT(caller_frame != NULL);
   const Code& orig_stub = Code::Handle(
       isolate->debugger()->GetPatchedStubAddress(caller_frame->pc()));
   const Error& error = Error::Handle(isolate->debugger()->SignalBpReached());
   if (!error.IsNull()) {
     Exceptions::PropagateError(error);
     UNREACHABLE();
   }
   arguments.SetReturn(orig_stub);
 }
 
 
 DEFINE_RUNTIME_ENTRY(SingleStepHandler, 0) {
   if (!FLAG_support_debugger) {
     UNREACHABLE();
+    return;
   }
   const Error& error =
       Error::Handle(isolate->debugger()->DebuggerStepCallback());
   if (!error.IsNull()) {
     Exceptions::PropagateError(error);
     UNREACHABLE();
   }
 }
 
 
@@ skipping 1158 matching lines @@
   const intptr_t elm_size = old_data.ElementSizeInBytes();
   const TypedData& new_data =
       TypedData::Handle(TypedData::New(cid, new_size, Heap::kOld));
   TypedData::Copy(new_data, 0, old_data, 0, old_size * elm_size);
   typed_data_cell.SetAt(0, new_data);
   arguments.SetReturn(new_data);
 }
 
 
 }  // namespace dart