- Added a new `-j` option to `gem install` and `gem update`.
This option allows to specify the number of jobs we pass to `make`
when compiling gem with native extensions.
By default its the number of processors, but users may want a way
to control this.
You can use it like so: `gem install json -j8`
https://github.com/ruby/rubygems/commit/67aad88ca6