gentoo-overlay/xfce-extra/xfce4-taskmanager/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <maintainer>
    <email>xfce@gentoo.org</email>
    <name>XFCE Team</name>
  </maintainer>
  <use>
	  <flag name='gksu'>Build against <pkg>x11-libs/libgksu</pkg> to provide "Run as root" option in the application's menu</flag>
	  <flag name='gtk3'>Use GTK+3 instead of GTK+2</flag>
  </use>
</pkgmetadata>