Remove orphaned check files and flags files.

    (for f in $(find test -name '*.check' -o -name '*.flags'); do bare=$(echo $f | sed -E 's/\.\w+$//'); ([[ -f "$bare" ]] || [[ -d "$bare" ]] || [[ -f "$bare.scala" ]] || [[ -f "$bare.test" ]] || echo $f) done;) | xargs rm