gentoo-overlay/sys-kernel/bliss-kernel-bin/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
    <!--maintainer-needed-->
    <use>
        <flag name='initramfs'>Build initramfs along with the kernel.</flag>
    </use>
</pkgmetadata>