Ruby's standard library has been going through a process of "gemification" where it is converted into a set of Gems that are simply vendored into the main Ruby distribution.
GNU/Linux distros tend to like to de-vendor things. This de-vendoring process is usually inherently a little messy. This MR tries to make it a little less messy in the case of Ruby on Arch Linux and downstream distros.
Besides hopefully making things easier on the Arch devs in the future, it should also make it easier for downstream distros that patch Ruby, such as applying flori/json#567.