**Is your feature request related to a problem? Please describe.** I can run `nix build .?submodules=1` but not declare that inside the `flake.nix` **Describe the solution you'd like** A top-level attribute `submodules = true;` inside the flake. **Describe alternatives you've considered** Stop using submodules. **Additional context** Maybe this should be the default? **Priorities** :+1: