Comment by defer

This is hilarious to me:

  Android, which uses it for some large component of the system that I've never quite understood

Ninja is really a huge part of AOSP, the build system initially used makefiles. Things got complex really fast with a custom declarative build system (soong) and a failed/aborted migration to bazel. Google developed kati (https://github.com/google/kati) which converts Makefiles to ninja build files (or should I say file), which really is huge:

  λ wc -l out/build-qssi.ninja    
    3035442 out/build-qssi.ninja

Going from makefiles/soong to ninja is painful, it takes several minutes even in a modern machine but it simply flies once ninja picks it up.