This project is used to have a library that is compiled with AGP 3.3.1. We don't compile it as part of tests since the goal is to have a project compiled with an old version.
Currently, it is in MultiModuleTestApp to reproduce b/122936785. If you wish to modify this, don't forget to update the aar in MultiModuleTestApp/app/libs.
./gradlew assemble && cp library/build/outputs/aar/library.aar ../MultiModuleTestApp/app/libs/lib_compiled_with_v2_agp_3_3_1.aar