I did use the prefix command i am installing using source code.
It is customary to bottom or inline posts on these lists.
Lacking experience myself, and specifics on your part, I'm not going to be able to help further without digging deeper into source code installation than I am able to at the moment. Someone else may though.
But, did you go look to the place where the default prefix would end up placing the docs, if you installed them at all?
David J.