gentoo-overlay/sys-apps/shadow/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<herd>base-system</herd>
<herd>pam</herd> <!-- only for USE=pam -->
<use>
 <flag name='audit'>Enable support for <pkg>sys-process/audit</pkg></flag>
 <flag name='tcb'>Enable support for <pkg>sys-auth/tcb</pkg></flag>
</use>
</pkgmetadata>