net/freeswitch: Fix build and disable -Werror to stop collecting -Wno-* flags
sip_pref_util.c:328:12: error: adding 'int' to a string does not append to the string [-Werror,-Wstring-plus-int]
base = MATCH("audio") || MATCH("automata") || MATCH("application") ||
^~~~~~~~~~~~~~sip_pref_util.c:315:31: note: expanded from macro 'MATCH'
(su_casenmatch(param + 1, s + 1, strlen(s) - 1) && \
~~^~~