build fix

src/server/game/Entities/Creature/Creature.h

@@ -126,13 +126,7 @@ class TC_GAME_API Creature : public Unit, public GridObject<Creature>, public Ma
         using Unit::SetImmuneToNPC;
         void SetImmuneToNPC(bool apply) override { Unit::SetImmuneToNPC(apply, HasReactState(REACT_PASSIVE)); }
 
-        void SetUnkillable(bool unkillable)
-        {
-            if (unkillable)
-                _staticFlags |= CREATURE_STATIC_FLAG_UNKILLABLE;
-            else
-                _staticFlags &= ~CREATURE_STATIC_FLAG_UNKILLABLE;
-        }
+        void SetUnkillable(bool unkillable) { _staticFlags.ApplyFlag(CREATURE_STATIC_FLAG_UNKILLABLE, unkillable);}
 
         /// @todo Rename these properly
         bool isCanInteractWithBattleMaster(Player* player, bool msg) const;