message: Remove the source archive functionality of ArchiveWriter
  We now build archives through strictly additive means rather than taking
  an existing archive and potentially substracting parts.
diff: @@ -30,25 +30,7 @@ pub(crate) struct ArArchiveBuilder<'a> {
  }
  impl<'a> ArchiveBuilder<'a> for ArArchiveBuilder<'a> {
  - fn new(sess: &'a Session, output: &Path, input: Option<&Path>) -> Self {
  - let (src_archives, entries) = if let Some(input) = input {
  - let read_cache = ReadCache::new(File::open(input).unwrap());
  - let archive = ArchiveFile::parse(&read_cache).unwrap();
  - let mut entries = Vec::new();
  -
  - for entry in archive.members() {
  - let entry = entry.unwrap();
  - entries.push((
  - entry.name().to_vec(),
  - ArchiveEntry::FromArchive { archive_index: 0, file_range: entry.file_range() },
  - ));
  - }
  -
  - (vec![read_cache.into_inner()], entries)
  - } else {
  - (vec![], Vec::new())
  - };
  -
  + fn new(sess: &'a Session, output: &Path) -> Self {
  ArArchiveBuilder {
  sess,
  dst: output.to_path_buf(),
  @@ -56,8 +38,8 @@ fn new(sess: &'a Session, output: &Path, input: Option<&Path>) -> Self {
  // FIXME fix builtin ranlib on macOS
  no_builtin_ranlib: sess.target.is_like_osx,
  - src_archives,
  - entries,
  + src_archives: vec![],
  + entries: vec![],
  }
  }
  