debian: don't try to build non-dfsg modules

debian/bootstrap.sh

@@ -17,7 +17,9 @@ avoid_mods=(
   applications/mod_skel
   asr_tts/mod_cepstral
   codecs/mod_com_g729
+  codecs/mod_ilbc
   codecs/mod_sangoma_codec
+  codecs/mod_siren
   codecs/mod_skel_codec
   codecs/mod_voipcodecs
   endpoints/mod_gsmopen