ngtcp2-gnutls: add passthru.tests

pkgs/development/libraries/ngtcp2/gnutls.nix

@@ -1,7 +1,7 @@
 { lib, stdenv, fetchFromGitHub
 , autoreconfHook, pkg-config
 , gnutls
-, cunit, ncurses
+, cunit, ncurses, knot-dns
 }:
 
 stdenv.mkDerivation rec {
@@ -27,6 +27,8 @@ stdenv.mkDerivation rec {
   checkInputs = [ cunit ]
     ++ lib.optional stdenv.isDarwin ncurses;
 
+  passthru.tests = knot-dns.passthru.tests; # the only consumer so far
+
   meta = with lib; {
     homepage = "https://github.com/ngtcp2/ngtcp2";
     description = "an effort to implement RFC9000 QUIC protocol.";