message: Pass -Zunstable-args in case `metadata` doesn't
diff: @@ -583,7 +583,7 @@ impl RustwideBuilder {
  cargo_args.push("--verbose".into());
  // We know that `metadata` unconditionally passes `-Z rustdoc-map`.
  // Don't copy paste this, since that fact is not stable and may change in the future.
  - // Normally we would need -Z unstable-options, but we currently pass that too.
  + cargo_args.push("-Zunstable-options".into());
  cargo_args.push(r#"--config=doc.extern-map.registries.crates-io="https://docs.rs""#.into());
  if let Some(cpu_limit) = self.config.build_cpu_limit {
  cargo_args.push(format!("-j{}", cpu_limit));
  