ruby: replace bundled RubyGems with our RubyGems
ruby: replace bundled RubyGems with our RubyGems

This should prevent problems caused by trying to install our own
RubyGems over the top of the one that comes with Ruby.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs