sys-apps/nix: new package, The Purely Functional Package Manager

sys-apps/nix: new package, The Purely Functional Package Manager

Nix is a source-based package manager with strong support for
binary packages. It uses multiple tricks to make package
source dependencies robust:

- nix installs every package into it's own --prefix=.
  Example: /nix/store/xsqz79bzclgrgnnlffp3qa0g4wnbcrp1-firefox-50.1.0
- nix builds packages with PATH (and similar) only including explicitly
  listed depends. This eliminates automagic dependency.
- nix tracks full environment where package was built.
  Once environment changes new package needs to be built.

That's how you install firefox just for your current user:

    $ nix-env -iA nixpkgs.firefox

Package-Manager: Portage-2.3.3, Repoman-2.3.1