“You must use Linux”

Made me smile:

“This section describes how to set up your local work environment to build the Android source files. You must use Linux; building under either MacOS or Windows isn’t supported. Keep in mind the important change to the /usr/bin/python binary as well.”

https://source.android.com/docs/setup/build/initializing

And yes, that’s Google, on how to build your own version of Android for phones or tablets…