extras: tools: use the ninja fork from Kitware with jobserver support

This work, from the CMake makers, supports jobserver and is actively maintained for many years.

The lack of jobserver support in the regular ninja is a problem when you're short on memory and have many threads available. It can explode the number of compilation threads running at more (X times the max of your CPU).

For now the CI won't benefit from it as we normally have ninja in the Docker images.