The ninja module is used pervasively in local development but isn't used in the build system, so this leaves it fragile and easily broken. We should either add a trivial test to the build system to detect when commits break ninja, or we should take steps to eliminate the desire of engineers to use it.
It is my understanding that most engineers use ninja because ninja offers a no-op build time that is exceptionally faster than the current scons no-op build time, but there could be other reasons as well.