let concat ~(run_with : Machine.t) bunch_of_files ~result_path =     let open KEDSL in     let program =       Program.(         exec ["mkdir"; "-p"; Filename.dirname result_path]         && shf "cat %s > %s"           (List.map bunch_of_files              ~f:(fun o -> Filename.quote o#product#path)            |> String.concat ~sep:" ") result_path       ) in     let name =       sprintf "concat-all-%s" (Filename.basename result_path) in     workflow_node       (single_file result_path ~host:Machine.(as_host run_with))       ~name       ~edges:(         on_failure_activate Remove.(file ~run_with result_path)         :: List.map ~f:depends_on bunch_of_files)       ~make:(Machine.run_stream_processor run_with ~name  program)