new ninja binaries

Hi,

we pushed new ninja binaries, you'll get them the next time you run gclient
(no need to run `gclient sync`: any gclient command will autoupdate
depot_tools, and ninja is in depot_tools). If `ninja --version` says
"1.5.1", you have the new version, if it says "1.4.0" you're still on the
old version. The waterfalls look green, so ideally things should just
continue working like they did – but if you run into any new ninja-related
issues, please file a bug on me.

Nico