(ruby-modules/gem): (refactor) (#53525)

* Changing leaveDotGit to git chacha on build

* Removing debugging cruft

* Simpler git handling

* Can't clobber index after `add`

* Update pkgs/development/ruby-modules/gem/default.nix

Useful comments

Co-Authored-By: nyarly <nyarly@users.noreply.github.com>

* Update pkgs/development/ruby-modules/gem/default.nix

Comments are useful

Co-Authored-By: nyarly <nyarly@users.noreply.github.com>