I would argue that what’s exposed in / should be consistent between NixOS and the build environment, which already isn’t the case. Adding more variations only makes these kind of build issues more confusing and difficult to reproduce.
- nixos
/bin/shand/usr/bin/env - builds
/bin/shand no env
A great example of the kind of issues that implicit impurities can introduce git: 2.16.2 -> 2.17.0 by layus · Pull Request #38636 · NixOS/nixpkgs · GitHub.