message: fix setting the manifest path manually when using cargo miri
diff: @@ -75,7 +75,9 @@ fn get_arg_flag_value(name: &str) -> Option<String> {
  fn list_targets() -> impl Iterator<Item=cargo_metadata::Target> {
  // We need to get the manifest, and then the metadata, to enumerate targets.
  - let manifest_path = get_arg_flag_value("--manifest-path").map(PathBuf::from);
  + let manifest_path = get_arg_flag_value("--manifest-path").map(|m|
  + Path::new(&m).canonicalize().unwrap()
  + );
  let mut metadata = if let Ok(metadata) = cargo_metadata::metadata(
  manifest_path.as_ref().map(AsRef::as_ref),
  