[build] Fix test build failure due to use of polymorphic compare

Reviewed By: skcho

Differential Revision: D20067724

fbshipit-source-id: f873cf937

infer/src/nullsafe/modelTables.ml

@@ -243,7 +243,7 @@ let nullable_method_with_nonnull_alternatives_nullability_list =
       ~f:(fun (nullability, method_descr, _) -> (nullability, method_descr))
   in
   List.iter result ~f:(fun ((ret_nullability, _param_nullability), _) ->
-      if not (ret_nullability == n) then
+      if not (Bool.equal ret_nullability n) then
         Logging.die Logging.InternalError "Function is expected to be nullable" ) ;
   result