postmodern/ruby-install — pull request #95 by Sirupsen (2013-11-14 18:02:59+00:00)
Title: Add parallel building of rubies

The `cores()` function is stolen from ruby-build
(https://github.com/sstephenson/ruby-build) and should work for both Linux and
OS X.

`--jobs` is a parameter from `make`:

> Specifies the number of jobs (commands) to run simultaneously.

This allows compiling more than one file at once.