gentoo-overlay/sys-fs/squashfs-tools/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <herd>livecd</herd>
  <use>
    <flag name="xz">Enable support for XZ ("LZMA2") compression using <pkg>app-arch/xz-utils</pkg></flag>
    <flag name="lz4">Enable support for LZ4 compression using <pkg>app-arch/lz4</pkg></flag>
  </use>
</pkgmetadata>