Make sass work when symlinked by encap.

The sass binaries don't work for when I set them up as encap packages, because of the odd way they handle symlinks. This change makes them work again.

FWIW, this is what I use for my setup. It worked with Sass 3.1.19 on top of MRI 1.9.3p194, but doesn't work on 3.2.9 on top of MRI 2.0.0p195.
https://gist.github.com/pwnall/3017424#file-build_ruby-sh
https://gist.github.com/pwnall/3017424#file-build_sass-sh

Thank you!