Jamba is using 3.6.9 and does it automatically for you. You may want to check how I did it jamba/audio-unit at master · pongasoft/jamba · GitHub
The main CMake file is jamba/jamba.cmake at v4.4.0 · pongasoft/jamba · GitHub
An easy way to see it in action is to go to Web - Jamba generate a dummy plugin, follow the instructions to configure and then you can run ./jamba.sh build-au
Yan