Fix #35681: cycles excluded layers still got evaluated before and after

rendering even if they were not used on any render layers.

source/blender/render/extern/include/RE_engine.h

@@ -56,6 +56,7 @@ struct Scene;
 #define RE_USE_PREVIEW			4
 #define RE_USE_POSTPROCESS		8
 #define RE_USE_SHADING_NODES	16
+#define RE_USE_EXCLUDE_LAYERS	32
 
 /* RenderEngine.flag */
 #define RE_ENGINE_ANIMATION		1