message: fix compile error newly introduced
diff: #include <ios> // std::ios_base::failure
  /// \endcond
  +#if __cplusplus >= 201703L
  +#include <filesystem>
  +#endif
  +
  namespace adios2
  {
  namespace transport
  @@ -354,10 +358,6 @@ void FileFStream::Seek(const size_t start)
  }
  }
  -#if __cplusplus >= 201703L
  -#include <filesystem>
  -#endif
  -
  void FileFStream::Truncate(const size_t length)
  {
  #if __cplusplus >= 201703L
  @@ -365,8 +365,9 @@ void FileFStream::Truncate(const size_t length)
  WaitForOpen();
  std::filesystem::path p(m_Name);
  std::filesystem::resize_file(p, static_cast<std::uintmax_t>(length));
  - CheckFile("couldn't move to offset " + std::to_string(start) + " of file " +
  - m_Name + ", in call to fstream seekp");
  + // TODO: variable start has not been defined...
  + // CheckFile("couldn't move to offset " + std::to_string(start) + " of file
  + // " + m_Name + ", in call to fstream seekp");
  #else
  // Trunation is not supported in a portable manner pre C++17
  #endif
  