I will have to update the documentation, in latest fpcupdeluxe embedded-mir was renamed to embedded and lazarus trunk now has all the needed changes that are necessary and embedded for lazarus was removed by Don Alfredo...
Choosing embedded for fpc and trunk for lazarus should do the trick.
The error you see is likely unrelated to your choices, I think I today read somewhere else that lazarus trunk itself has build issues atm, seems I was lucky when tesing latest fpcupdeluxe release on my Mac yesterday, then all still worked fine.