NixOS/nixpkgs — pull request #229 by viric (2012-12-26 21:28:45+00:00)
Title: Allow /niximpure/impure.sh impurity, only for users wanting it

Coming from my previous pull request about this (https://github.com/NixOS/nixpkgs/pull/228), niksnut was against it because it introduces a big source of impurity for everyone.

This new approach makes a 'setup.sh' considering /niximpure/impure.sh only if it has been set in the platform, and the impure derivations coming from that stdenv will all have a different hash compared to the canonical setup.sh.