- Introduce tests/e2e/test_nix_build_pkgmgr.py to inspect the Nix environment
and build the pkgmgr flake inside the container started by test-e2e.sh
- Run the same commands in every distro container: nix --version, sandbox
config, id, and nix build .#pkgmgr -L
- Print stdout/stderr and assert the flake build succeeds for easier
cross-distro Nix debugging
https://chatgpt.com/share/693aa33f-4e3c-800f-86ec-99c38a07eacb
