add ISync to all traits that have [Sync] members

OpenRA.Mods.RA/Buildings/RepairableBuilding.cs

@@ -20,9 +20,9 @@ namespace OpenRA.Mods.RA.Buildings
 		public readonly float RepairRate = 0.016f;
 		public readonly int RepairStep = 7;
 		public object Create(ActorInitializer init) { return new RepairableBuilding(init.self, this); }
-	}
-
-	public class RepairableBuilding : ITick, IResolveOrder
+	}
+
+	public class RepairableBuilding : ITick, IResolveOrder, ISync
 	{
 		[Sync]
 		bool isRepairing = false;