message: Apply mmstick's tip
diff: @@ -564,9 +564,9 @@ fn spawn_proc(
  let mut command = Command::new(&args[0].as_str());
  command.args(args[1..].iter().map(types::Str::as_str));
  - command.stdin(stdin.map(Into::into).unwrap_or_else(Stdio::inherit));
  - command.stdout(stdout.map(Into::into).unwrap_or_else(Stdio::inherit));
  - command.stderr(stderr.map(Into::into).unwrap_or_else(Stdio::inherit));
  + command.stdin(stdin.map_or_else(Stdio::inherit, Into::into));
  + command.stdout(stdout.map_or_else(Stdio::inherit, Into::into));
  + command.stderr(stderr.map_or_else(Stdio::inherit, Into::into));
  let pgid_copy = *pgid;
  command.before_exec(move || sys::setpgid(0, pgid_copy));
  