gentoo-overlay/dev-libs/xerces-c/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "https://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<!-- maintainer-needed -->
<use>
  <flag name="iconv">Use iconv (<pkg>virtual/libiconv</pkg>) as message loader
    and transcoder (in general it would be possible to use iconv only as
    message loader and something else like icu or the native method as
    transcoder and vice-versa, but this is a less common case and hard to
    handle)</flag>
  <flag name="threads">Enable threading support through pthread (or other
    libraries on AIX, IRIX, HPUX, Solars). Highly recommended</flag>
</use>
</pkgmetadata>