Ninja. For the time being, build openclonk without Ninja--I've spent all day running and rerunning builds with USE_NINJA=No and haven't hit any failures. I will track this down and figure it out, but for now add a USE_NINJA=No line so that I'm not bothering the bulk builders. While here, add myself as MAINTAINER (oversight) and bump. Build failure spotted by naddy@, thanks.