I did. I wrote it in assembly for a larp. It didn't do anything useful other than boot. It's pretty easy, and you only really need a hex editor.
I'd be interested in detailed Android app making guides without an IDE. All the app code repos I view have a lot of useless extra files to serve the IDE. I've made a couple of apps so far from the command line, but growing them is trial and error.
An android app is merely a few XML files with a sprinkling of Java on top, but even the official documentation expects you to be using an IDE.
sage for a thread as shit as the OS I made.