enable ccacheStdenv on nix.sharcnet.ca
It would be nice when working on a package to be able to use the ccacheStdenv
(while technically not secure as a previous build could put a trojan in the cache, this would only effect people who deliberately use it and thus are presumably aware of the risk). This would require setting up an appropriate directory on nix.sharcnet.ca, setting it to be mounted in the rooted environments, and adjusting the ccacheStdenv configuration to use it.