Hey Rodney,
Yes, libexpat has been ported already, you can find it in the contrib dir, indeed.
About the buffer overflow... what exactly do you mean? Is it an error the shell report? If so, then it must be because our shell doesn't handle paths longer than 256 characters (I know, this is a limitation which I always forget we have... need to find the time to fix it), and it might be that the current pathname lenght is longer than the maximum. Try renaming the contrib dir from its name to just "contrib", and see if things change.