Upgrade to Ninja 1.13.1

[segevfiner]

Ninja 1.13.1 is available and it includes a new jobserver implementation so we probably don't even need a fork of Ninja anymore? (Unless the Kitware fork will pick up some new PR that we will want, e.g. Some missing jobserver functionality and so on). Might want to update this to the latest official Ninja?

[mayeut]

The fork is still needed c.f. #305
1.13.1 from kitware might be available at a later date (c.f. Kitware/ninja#3 (comment))

[henryiii]

TL;DR: The fork supports older versions of Make vs. the official jobserver implementation, which requires a very new version. Once we don't care about older versions of Make, the fork can be dropped.

[henryiii]

1.13.0 is out. Leaving this open since 1.13.1 is not available in the fork yet.

[ScottTodd]

FYI Ninja 1.13.0 is affected by ninja-build/ninja#2616 which breaks various builds on Windows. I've had to unpin ninja in a few repositories to avoid the broken release and it looks like others have had to do the same. A more comprehensive testing and rollout plan would be appreciated, since debugging has caused substantial churn.