Although this function is introduced in here(https://doc.qt.io/qt-6/quick3d-asset-conditioning-ibl.html#build-time-baking-via-cmake), this is not documented. 
I've used this and the generated ktx yielded a lighting with horrible quality which made me assume there are parameters I can specify to this cmake function, but I couldn't find the documentation. Our users may find themselves in the same situation.