Provide docs on how to use jobserver with ninja (fork)
There's a fork of Ninja on the Kitware Github that has the Ninja jobserver PR merged: https://github.com/Kitware/ninja. This makes me think that it's possible to use CMake with this Ninja fork to allow Ninja to use a jobserver when running ExternalProject superbuilds. However, I can't find any documentation anywhere on how to make this work. Is it possible to add docs on how to do this if it's supported?