message: Fix MLIR Build after LLVM upstream JIT changes (getMainJITDylib removed)
  The getMainJITDylib() method was removed in replace it by creating a JITDylib on the fly.
diff: @@ -234,9 +234,12 @@ Expected<std::unique_ptr<ExecutionEngine>> ExecutionEngine::create(
  auto objectLayer = std::make_unique<RTDyldObjectLinkingLayer>(
  session, []() { return std::make_unique<SectionMemoryManager>(); });
  auto dataLayout = deserModule->getDataLayout();
  + llvm::orc::JITDylib *mainJD = session.getJITDylibByName("<main>");
  + if (!mainJD)
  + mainJD = &session.createJITDylib("<main>");
  // Resolve symbols that are statically linked in the current process.
  - session.getMainJITDylib().addGenerator(
  + mainJD->addGenerator(
  cantFail(DynamicLibrarySearchGenerator::GetForCurrentProcess(
  dataLayout.getGlobalPrefix())));
  