31/10/2019: ninja replaced by samurai
The build tool ninja has been replaced with samurai.
This replacement is 1:1 compatible with ninja, absolutely tiny in
size, doesn't require python to build and is simply simpler.
The one downside is that a smidgen of manual intervention is required.
Simply remove ninja (KISS_FORCE=1 kiss r ninja) and run
kiss update.
The sources for Samurai can be found here: https://github.com/michaelforney/samurai