make-temp-dir should behave similarly to rm -rf, not just rmdir

[AlexDaniel]

https://github.com/perl6/roast/blob/104173b332cdffcdcfd9bb76a1d85abdc9f4a273/packages/Test/Util.pm#L262-L267

So if you create a directory with make-temp-dir, and then add some files to it, it won't be deleted when the test file is finished (because rmdir can only delete empty directories).