Fixed some clang warnings

src/libslic3r/GCode.cpp

@@ -891,6 +891,7 @@ namespace DoExport {
     }
 }
 
+#if 0
 // Sort the PrintObjects by their increasing Z, likely useful for avoiding colisions on Deltas during sequential prints.
 static inline std::vector<const PrintInstance*> sort_object_instances_by_max_z(const Print &print)
 {
@@ -903,6 +904,7 @@ static inline std::vector<const PrintInstance*> sort_object_instances_by_max_z(c
             instances.emplace_back(&object->instances()[i]);
     return instances;
 }
+#endif
 
 // Produce a vector of PrintObjects in the order of their respective ModelObjects in print.model().
 std::vector<const PrintInstance*> sort_object_instances_by_model_order(const Print& print)