docs: def get_build_file_path(self, build_module) -> str:
          """Return a full path to the build file of `build_module`.
  
          The returned path will always be OS-native, regardless of the format
          of project_root (native) and build_module (with '/').
          """
          project_root = Path(self.project_root)
          build_module = norm_proj_path(build_module, '')
          return str(project_root / build_module /
                     (BUILD_PROJ_FILE if '' == build_module
                      else self.build_file_name))