gentoo-overlay/sys-freebsd/freebsd-sources/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<maintainer type="project">
    <email>bsd@gentoo.org</email>
    <name>BSD Project</name>
  </maintainer>
  <use>
    <flag name="build-kernel">Build and install a kernel (recommended).</flag>
    <flag name="dtrace">Enable DTrace support.</flag>
    <flag name="zfs">Enable ZFS support.</flag>
  </use>
</pkgmetadata>