EBUSY occurs if xbps tries to remove a directory with unlink(2) that is
a mount point, this happens with `/boot` as example.
https: //github.com/voidlinux/void-packages/issues/7229#issuecomment-319392560
https: //github.com/voidlinux/void-packages/issues/8753
Closes: #259 [via git-merge-pr]