Please consider adding realpath to posix. If I understand correctly realpath is a specified part of posix and thus would quite naturally fit into the posix unit. I think it is a very handy routine and I use it extensively. Then again, perhaps most sane environments don't have the tangle of symlinks that I have to contend with.
Note that normalize-path is not the same as realpath and that although realpath would be nice to have calling the system realpath works just fine and so this is a suggestion and not a request ....
I did take a look at the posixunix.c code and at using easyffi or bind and quickly concluded that for the moment at least it is safer for me to keep using the system realpath :)