adding a build.gradle for projects that don't have one So we can start to rely on each project having a build.gradle, so when we start to look for a build.gradle we can be more confident that we computed the path (at which to look) correctly Bug: 271282538 Test: Needed by later change Test: Treehugger runs busytown/*.sh Change-Id: I4b125cee06352db4c837713928f37e8327d0def5