let star =
  let url = "https://github.com/alexdobin/STAR/archive/STAR_2.4.1d.tar.gz" in
  let star_binary = "STAR" in
  (* TODO: there are other binaries in `bin/` *)
  let star_binary_path = sprintf "bin/Linux_x86_64/%s" star_binary in
  installable_tool ~url Machine.Tool.Default.star
    ~init_program:add_to_dollar_path
    ~unarchived_directory:"STAR-*"
    ~install_program:KEDSL.Program.(fun ~path ->
        shf "cp %s %s" star_binary_path path)
    ~witness:(witness_file star_binary)