Ok, thanks for the suggestions. I have edited a little bit the page, following your advices

The error you get comes in two cases: 1) the rtl isn't built at all or it misses some units or 2) the file fpc.cfg is missing or it points to the wrong paths.
Please, make sure that in C:\fpc4wii\units\powerpc-wii there are system.o and system.ppu.

In the meanwhile, I just found some problems (a couple of functions I forgot to translate...) on libogcfpc. Please, download gccore.inc again from the svn trunk