augenrules: fixes for non-FHS-compliant systems

[LordGrimmauld]

These changes are useful on FHS-noncompliant systems, such as NixOS.

Currently, augenrules is just broken. In an effort to align our package more closely with upstream, i wanted to make use of this script. However, its reliance on absolute paths is a detriment to that effort, requiring some patching:

https://github.com/NixOS/nixpkgs/pull/441506/commits/d54599d8e5e9dde1fecabd23c810f1b7b04a542c

Prefixing $PATH is normal and common, but i would rather we don't need to replace paths to auditctl and ls.