Build regularly as you would any other app with Android studio. targetSdkVersion must not be higher than 22 because of some security changes that have been made in higher versions.
Just install the app and enter the desired value to adjust the auto brightness and click OK. This app will set the brightness every time the screen is turned on (the adjustment value doesn't seem to stick), and it also starts at boot, though for some reason it doesn't set the brightness then (if anyone knows the reason let me know), just lock and unlock the phone for it to take effect.
