// this file always exists.
let need_metadata_file = tcx.sess.opts.output_types.contains_key(&OutputType::Metadata);
let (metadata_filename, metadata_tmpdir) = if need_metadata_file {
// this file always exists.
let need_metadata_file = tcx.sess.opts.output_types.contains_key(&OutputType::Metadata);
let (metadata_filename, metadata_tmpdir) = if need_metadata_file {