Fix DBC product build

runtime/vm/simulator_dbc.cc

 // Copyright (c) 2016, 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 <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_DBC)
 
@@ skipping 1111 matching lines @@
     if (thread->isolate()->single_step()) {
       Exit(thread, FP, SP + 1, pc);
       NativeArguments args(thread, 0, NULL, NULL);
       INVOKE_RUNTIME(DRT_SingleStepHandler, args);
     }
     DISPATCH();
   }
 
   {
     BYTECODE(DebugBreak, A);
+#if !defined(PRODUCT)
     {
       const uint32_t original_bc =
           static_cast<uint32_t>(reinterpret_cast<uintptr_t>(
               thread->isolate()->debugger()->GetPatchedStubAddress(
                   reinterpret_cast<uword>(pc))));
 
       SP[1] = null_value;
       Exit(thread, FP, SP + 2, pc);
       NativeArguments args(thread, 0, NULL, SP + 1);
       INVOKE_RUNTIME(DRT_BreakpointRuntimeHandler, args)
       DISPATCH_OP(original_bc);
     }
+#else
+    // There should be no debug breaks in product mode.
+    UNREACHABLE();
+#endif
     DISPATCH();
   }
 
   {
     BYTECODE(InstantiateType, A_D);
     RawObject* type = LOAD_CONSTANT(rD);
     SP[1] = type;
     SP[2] = SP[0];
     SP[0] = null_value;
     Exit(thread, FP, SP + 3, pc);
@@ skipping 766 matching lines @@
   special_[kExceptionSpecialIndex] = raw_exception;
   special_[kStacktraceSpecialIndex] = raw_stacktrace;
   buf->Longjmp();
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 
 #endif  // defined TARGET_ARCH_DBC