fix #4577

Author: lperron

ortools/flatzinc/mznlib/fzn_disjunctive_opt.mzn

@@ -1,4 +1,6 @@
+include "fzn_cumulative_opt.mzn"
+
 predicate fzn_disjunctive_opt(array[int] of var opt int: s,
                               array[int] of var int: d) =
         forall(i in index_set(d))(d[i] >= 0)
-    /\  fzn_cumulative_opt(s, d, [1 | i in index_set(s)], 1);
+    /\  fzn_cumulative_opt(s, d, [1 | i in index_set(s)], 1);