Trying to create a simple flake with input:
```
{
inputs.nixpkgs-lib.url = "github:NixOS/nixpkgs?dir=lib";
outputs = {nixpkgs-lib, ...}: { };
}
```
Fails when trying to evaluate the nixpkgs-lib flake with an error like:
```
error: getting status of '/nix/store/xxxx-source/lib/lib': No such file or directory
(use '--show-trace' to show detailed location information)
```
A subflake that can be indidividually accessed without also providing
an interface to the whole of nixpkgs.
Usage:
inputs.nixpkgs-lib.url = "github:NixOS/nixpkgs?dir=lib"