optional_depends libxml2 \
                 "--with-libxml2" \
                 "--without-libxml2" \
                 "to use libxml2 instead of expat for XML parsing" &&

if ! is_depends_enabled ${SPELL} libxml2; then
  depends expat
fi &&

optional_depends SSL \
                 "--enable-tls" \
                 "--disable-tls" \
                 "for TLS support"