Missing /bin/sh on live image

I’ve been helping a friend debug some issues with their NixOS live image their building with parts of their config integrated. I had a “well that’ll do it” moment when I realized that /bin/sh was completely absent when the image was booted. To be clear: Not a broken symlink, just completely not there: /bin/ is an empty folder. My normal debugging approaches would be one of either: A) creating a minimal reproducer, or B) digging into the Nix source code to figure out what options could cause ...