This repo contains the source of the substratum platform jar that resides inside of the Substratum app. In order to build and modify it, you must clone the source somewhere in an Android build environment (like external/libsubstratum) and run the following commands:
. build/envsetup.sh
lunch
make -j# libsubstratum_staticThen copy that into the Substratum repo (app/src/main/libs/libsubstratum.jar) and build the app to test.