message: Do not treat `warning` and `rerun-if-changed` as user-defined metadata in build script overrides
diff: @@ -505,6 +505,9 @@ fn scrape_target_config(config: &Config, triple: &str)
  let list = value.list(&k)?;
  output.cfgs.extend(list.iter().map(|v| v.0.clone()));
  }
  + "warning" | "rerun-if-changed" => {
  + bail!("`{}` is not supported in build script overrides", k);
  + }
  _ => {
  let val = value.string(&k)?.0;
  output.metadata.push((k.clone(), val.to_string()));
  