prompt: tweak conditional compilation so as not to trigger `unused_…

…mut` lint on Windows and Linux

thanks to @rzmk's PR - $1879

src/cmd/prompt.rs

@@ -159,15 +159,19 @@ pub fn run(argv: &[&str]) -> CliResult<()> {
  let title = args
  .flag_msg
  .unwrap_or_else(|| DEFAULT_OUTPUT_TITLE.to_owned());
- let mut fd = FileDialog::new()
+
+ #[cfg(not(target_os = "macos"))]
+ let fd = FileDialog::new()
  .set_directory(args.flag_workdir)
  .set_title(title)
  .set_file_name(args.flag_save_fname);
 
  #[cfg(target_os = "macos")]
- {
- fd = fd.set_can_create_directories(true);
- }
+ let fd = FileDialog::new()
+ .set_directory(args.flag_workdir)
+ .set_title(title)
+ .set_file_name(args.flag_save_fname)
+ .set_can_create_directories(true);
 
  // no delay here, we want the save dialog to appear immediately
  // the delay is only for input dialogs, so they pop over in reverse order