message: fix non-mpi build
diff: @@ -108,8 +108,10 @@ ProcessMetadata(int rank, const adios2::Engine &reader, adios2::IO &io,
  ADIOS2_FOREACH_TYPE_1ARG(declare_template_instantiation)
  #undef declare_template_instantiation
  }
  +#ifdef ADIOS2_HAVE_MPI
  // sync printouts
  MPI_Barrier(readerComm);
  +#endif
  return varinfos;
  }
  @@ -173,8 +175,8 @@ void SerialPrintout(std::vector<VarInfo> &varinfos, int rank, int nproc)
  std::this_thread::sleep_for(timespan);
  MPI_Send(&token, 1, MPI_INT, rank + 1, 0, readerComm);
  }
  -#endif
  MPI_Barrier(readerComm);
  +#endif
  }
  std::string argEngine = "BPFile";
  