svoid mergeJars_manifestFromFirst(File... insAndOut) {
  mergeJars_manifestFromFirst(dropLast(wrapAsList(insAndOut)), last(insAndOut));
}

svoid mergeJars_manifestFromFirst(L<File> in, File out) ctex {
  new Set<S> set;
  var it = iterator(in);
  if (!it.hasNext())
    fail("No input jars");
  {
    temp ZipOutputStream zip = newZipOutputStream(out);
    zip2zip_collectFiles(it.next(), zip, set);
    while (it.hasNext())
      zip2zip_exceptManifest2(it.next(), zip, set);
    zip.close();
  }
  print("Wrote " + f2s(out));
}

Began life as a copy of #1019059