The lib ones are from this: nixos/stub-ld: init module by tejing1 · Pull Request #269551 · NixOS/nixpkgs · GitHub
The /usr one is there exclusively to let us have /usr/bin/env as a common way to allow shebangs to work, e.g. #!/usr/bin/env bash at the top of a script.
/bin/sh is there because that’s how the system() function in libc works.