gentoo-overlay/dev-libs/gobject-introspection/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
<herd>gnome</herd>
<use>
	<flag name="doctool">Install g-ir-doc-tool for generating documentation
		from introspected data</flag>
</use>
</pkgmetadata>