removeDirectoryRecursive symlink TOCTOU

removeDirectoryRecursive and similar are supposed to avoid following symlinks. However, they all appear to have a TOCTOU flaw that exposes them to a race condition that could lead to deleting symlinked directory trees.

Ie, in a call `removePathRecursive "foo"`, if `foo` is a directory at the stat call, and then gets replaced with a symlink before removeContentsRecursive calls `listDirectory`, then it will get a list of the files in the symlinked directory, and proceed to delete them.

This could be a security problem if deleting a directory that is writable by another user, or perhaps by a containerized, untrusted process that has been given write access to the directory. Security aside, this kind of race can lead to unexpected data loss, though the probability of the right sequence of events is of course lower.

I checked how rm -r (from coreutils) handles this, and it uses open with `O_NOFOLLOW` when opening directories, and so avoids listing the contents of directory symlinks.

I think that a similar fix could work here, if `listDirectory` used `O_NOFOLLOW` it seems it would nicely solve the problem. (It would also speed it up by avoiding needing to stat every directory it traverses.)

openDirStream does not currently have a way to pass that flag, so it would need to be patched first.