Fix the compilation of gdbjit

src/gdb-jit.cc

 // Copyright 2010 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 2066 matching lines @@
                             info);
 
   if (!FLAG_gdbjit_full && !code_desc.IsLineInfoAvailable()) {
     delete lineinfo;
     GetEntries()->Remove(code, HashForCodeObject(code));
     return;
   }
 
   AddUnwindInfo(&code_desc);
   Isolate* isolate = code->GetIsolate();
-  Zone* zone = code->GetIsolate()->runtime_zone();
   JITCodeEntry* entry = CreateELFObject(&code_desc, isolate);
   ASSERT(!IsLineInfoTagged(entry));
 
   delete lineinfo;
   e->value = entry;
 
   const char* name_hint = NULL;
   bool should_dump = false;
   if (FLAG_gdbjit_dump) {
     if (strlen(FLAG_gdbjit_dump_filter) == 0) {
@@ skipping 73 matching lines @@
   ScopedLock lock(mutex.Pointer());
   ASSERT(!IsLineInfoTagged(line_info));
   HashMap::Entry* e = GetEntries()->Lookup(code, HashForCodeObject(code), true);
   ASSERT(e->value == NULL);
   e->value = TagLineInfo(line_info);
 }
 
 
 } }  // namespace v8::internal
 #endif