Logger: fix compilation

src/engine_maketasks.c

@@ -831,7 +831,9 @@ void engine_make_hierarchical_tasks_common(struct engine *e, struct cell *c) {
   const int with_timestep_limiter =
       (e->policy & engine_policy_timestep_limiter);
   const int with_timestep_sync = (e->policy & engine_policy_timestep_sync);
+#ifdef WITH_LOGGER
   const int with_logger = e->policy & engine_policy_logger;
+#endif
 
   /* Are we at the top-level? */
   if (c->top == c && c->nodeID == e->nodeID) {
@@ -1076,7 +1078,9 @@ void engine_make_hierarchical_tasks_hydro(struct engine *e, struct cell *c,
   const int with_cooling = (e->policy & engine_policy_cooling);
   const int with_star_formation = (e->policy & engine_policy_star_formation);
   const int with_black_holes = (e->policy & engine_policy_black_holes);
+#ifdef WITH_LOGGER
   const int with_logger = (e->policy & engine_policy_logger);
+#endif
 
   /* Are we are the level where we create the stars' resort tasks?
    * If the tree is shallow, we need to do this at the super-level if the