message: Disable preserving mtimes on archives
  These are just wasted syscalls for our purposes, no need to issue
  updates to the modification/creation/access times of files we unpack!
diff: @@ -463,6 +463,7 @@ impl<'cfg> RegistrySource<'cfg> {
  let gz = GzDecoder::new(tarball);
  let mut tar = Archive::new(gz);
  + tar.set_preserve_mtime(false);
  let prefix = unpack_dir.file_name().unwrap();
  let parent = unpack_dir.parent().unwrap();
  for entry in tar.entries()? {
  