Switch to use cmake on buildbot fails, ninja version at fault

Just a heads up in case any other buildbot maintainers are looking to switch to use cmake on their bots...

I switched one of the powerpc64 buildbots to use cmake and the runs failed with a really strange error (it couldn't figure out the size of pointers). After a lot of experimenting I finally figured out that the problem was with ninja. The source files that were being used to figure out system settings were weird gibberish instead of actual program text.

I built and installed a new version of ninja (1.6) to replace the system one (v1.5.8.1) and now everything works.