Download the sootclasses-trunk-jar-with-dependencies.jar file and save as soot.jar from https://soot-build.cs.uni-paderborn.de/public/origin/master/soot/soot-master/3.3.0/build/.
Run:
$ ./gradlew jimpleand hopefully jimple files will show up in sootOutput/.
For more information about what soot and jimple is, see https://github.com/soot-oss/soot