- Update test_nix_build_pkgmgr.py to invoke
nix --option sandbox false build .#pkgmgr -L
to avoid sandbox/permission issues in Debian and Ubuntu containers.
- Keeps the test logic identical across all distros while ensuring
consistent flake build behaviour during E2E runs.
https://chatgpt.com/share/693aa33f-4e3c-800f-86ec-99c38a07eacb