gentoo-overlay/app-misc/ca-certificates/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "https://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
	<maintainer type="project">
		<email>base-system@gentoo.org</email>
		<name>Gentoo Base System</name>
	</maintainer>
	<use>
		<flag name="cacert">
			Include root/class3 certs from CAcert (https://www.cacert.org/)
		</flag>
	</use>
</pkgmetadata>