fy enable option by using
`mkEnableOption`
(cherry picked from commit c4e4071ed115aca6ad8e7a15429638b2c497e790)
Commit: 1c5f4ae5d2813a631b2883b7b8beace0293cfac7
https://github.com/NixOS/nixpkgs/commit/1c5f4ae5d2813a631b2883b7b8beace0293cfac7
Author: Daniel Fullmer <danielr...@gmail.
Branch: refs/heads/master
Home: https://github.com/NixOS/nixpkgs
Commit: a8c738713bd13f13987bde696f1e811bc253e884
https://github.com/NixOS/nixpkgs/commit/a8c738713bd13f13987bde696f1e811bc253e884
Author: Daniel Fullmer <danielr...@gmail.com>
Date: 2017-02-20 (Mon, 20 Fe