New review comment by ahesford on void-packages repository

https://github.com/void-linux/void-packages/pull/43946#discussion_r1211768371

Comment:
I've been thinking about this some more and believe we should be more targeted in the removal:
```suggestion
	rm -r "${testdir}"
```
Yes, this will leave `tmp` around if we created it, but I suspect that won't cause any problems, and it might avoid a problem where a package actually ships a `tmp` directory.  What do you think?