Add the necessary scaffolding to add lief as a dependency.

• swap out some of the patchelf functionality for native cpython integration via lief
• remove coreutils since now we don't rely on bin/cp for copy (that was egregious)
• improve the poetry2nix setup after scouring GitHub for examples (Thank you @lovesegfault)
• add flake checks to make the CI process simpler and more robust
• remove patchelf