kati is an experimental GNU make clone. The main goal of this tool is to speed-up incremental build of Android.
Currently, kati does not offer a faster build by itself. It instead converts your Makefile to a ninja file.
For Android-N+, ckati and ninja is used automatically. There is a prebuilt checked in under prebuilts/build-tools that is used.
All Android's build commands (m, mmm, mmma, etc.) should just work.