Make the tool working even if there is a symlink in a given path to a port's
file. For example I'm usually keeping all working directories in /tmp using
WRKDIRPREFIX, while for the quick access to a port's files creating a symlink
to this directory in skeleton's dir (i.e. ports/foo/bar/src -->
/tmp/usr/ports/foo/bar/work/bar-0.0) and with this patch the tool correctly
works when I'm specifying `src/foo.c' as an argument.