os_hardening 2.4.0: better resiliency against looped symlinks like `/usr/bin/X11 -> ./`

[ped7g]

Running puppet agent after VSCode package update, I did notice minimize_access is going slightly deep into the rabbit hole /usr/bin/X11/X11/X11/...:

...
/Stage[main]/Os_hardening::Minimize_access/File[/usr/bin/X11/X11/X11/X11/code]/mode: mode changed '0775' to '0755' (go-w) (corrective)
...

$ ls -lad /usr/bin/X11
lrwxrwxrwx 1 root root 1 bře 14 10:32 /usr/bin/X11 -> .

After some googling it seems the /usr/bin/X11 linking to /usr/bin/ is regular way how things on Ubuntu are set up, but I'm a bit worried about the minimize_access script going unnecessarily deeply into this infinite cycle, I guess it would be nice to not follow X11 link at all (detecting that you are already going through the destination) or not more than once, ie. I would expect those permissions to be adjusted on /usr/bin/code or /usr/bin/X11/code.

This seems to be regression/change of #64 done in 2016 (I would guess it was intentional change and thus following symlinks is a feature?).

In ideal world maybe caching realpath of directories which are already being processed and rejecting processing the same one twice would make this more robust (and efficient maybe too? I guess it depends on how efficiently it's possible to get real/canonical path, in worst case this may cause overall load to increase).

(version used seems to be hardening-os_hardening 2.4.0 - I'm not sure how to verify that, got it from listing of dependencies)

edit: #116 seems to be another related change done in past, didn't notice this one before