Undefine HAVE_GETNAMEINFO if unable to find

proper types to use for getnameinfo args

acinclude.m4

@@ -277,6 +277,9 @@ AC_DEFUN([CURL_FUNC_GETNAMEINFO_ARGTYPES], [
   ])
   if test "$curl_cv_func_getnameinfo_args" = "unknown"; then
     AC_MSG_WARN([Cannot find proper types to use for getnameinfo args])
+    AC_MSG_WARN([Undefining HAVE_GETNAMEINFO])
+    undefine([HAVE_GETNAMEINFO])dnl
+    ac_cv_func_getnameinfo="no"
   else
     gni_prev_IFS=$IFS; IFS=','
     set dummy `echo "$curl_cv_func_getnameinfo_args" | sed 's/\*/\*/g'`