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
2 files changed