message: Don't call `to_string()` on &&str
diff: @@ -107,7 +107,7 @@ impl RustwideBuilder {
  let mut targets_to_install = TARGETS
  .iter()
  - .map(|t| t.to_string())
  + .map(|&t| t.to_string())
  .collect::<HashSet<_>>();
  let installed_targets = match self.toolchain.installed_targets(&self.workspace) {
  Ok(targets) => targets,
  @@ -209,7 +209,7 @@ impl RustwideBuilder {
  .iter()
  .map(|f| (f, true))
  .chain(ESSENTIAL_FILES_UNVERSIONED.iter().map(|f| (f, false)));
  - for (file, versioned) in files {
  + for (&file, versioned) in files {
  let segments = file.rsplitn(2, '.').collect::<Vec<_>>();
  let file_name = if versioned {
  format!("{}-{}.{}", segments[1], rustc_version, segments[0])
  