message: Disable IODI when the accompanying debug symbol files are not emitted
  Summary: With IODI we require these other files in order to function correctly. Rather than silently failing and later finding that we have a bum config let's emit diagnostics up front to warn the user right away.
diff: @@ -759,6 +759,14 @@ void redex_backend(const PassManager& manager,
  cfg.metafile(json_cfg.get("debug_line_method_map_v2", std::string()));
  auto iodi_metadata_filename =
  cfg.metafile(json_cfg.get("iodi_metadata", std::string()));
  + if ((debug_line_mapping_filename_v2.empty() || pos_output_v2.empty()) &&
  + !iodi_metadata_filename.empty()) {
  + fprintf(stderr,
  + "[WARNING] IODI will not be used because it requires"
  + " debug_line_method_map_v2 and line_number_map_v2 to be set"
  + " (these artifacts are required for leaveraging iodi_metadata)!\n");
  + iodi_metadata_filename = "";
  + }
  std::unique_ptr<PositionMapper> pos_mapper(
  PositionMapper::make(pos_output, pos_output_v2));
  