message: Fix debuginfo generation when given source path doesn't contain a dir (eg plain lib.rs)
diff: @@ -28,12 +28,17 @@ fn line_program_add_file(
  ) -> FileId {
  match file {
  FileName::Real(path) => {
  + let dir_name = path.parent().unwrap().to_str().unwrap().as_bytes();
  + let dir_id = if !dir_name.is_empty() {
  let dir_name = LineString::new(
  - path.parent().unwrap().to_str().unwrap().as_bytes(),
  + dir_name,
  line_program.encoding(),
  line_strings,
  );
  - let dir_id = line_program.add_directory(dir_name);
  + line_program.add_directory(dir_name)
  + } else {
  + line_program.default_directory()
  + };
  let file_name = LineString::new(
  path.file_name().unwrap().to_str().unwrap().as_bytes(),
  line_program.encoding(),
  