There should be no trick, just ensure the last test game you played had the lightmaps (PREBAKE) and then use Save Standalone. Your final executable should export with the lightmaps and your game should use them. If this still persists, send me a step by step from a fresh install of GameGuru using stock media and I can reproduce and see what you see (maybe even a video if you have bandicam).
PC SPECS: Windows 8.1 Pro 64-bit, Intel Core i7-5930K (PASSMARK:13645), NVIDIA Geforce GTX 980 GPU (PASSMARK:9762) , 32GB RAM
