message: Add rustdoc fingerprint exception for clean
diff: @@ -432,7 +432,7 @@ fn assert_all_clean(build_dir: &Path) {
  }) {
  let entry = entry.unwrap();
  let path = entry.path();
  - if let ".rustc_info.json" | ".cargo-lock" | "CACHEDIR.TAG" =
  + if let ".rustc_info.json" | ".cargo-lock" | "CACHEDIR.TAG" | ".rustdoc_fingerprint.json" =
  path.file_name().unwrap().to_str().unwrap()
  {
  continue;
  