bug: needless copy of nixpkgs

[nrdxp]

This line here:

microvm.nix/nixos-modules/host/options.nix

Line 41 in c4e4a26

merge = loc: defs: (import "${config.nixpkgs}/nixos/lib/eval-config.nix" {

Causes a needless recopying of nixpkgs to the store, even if it is already in the store. This is due to nix's behavior when using a path in interpolation. It automatically imports any interpolated paths to the /nix/store (strange I know, but that's what it does).

it's possible simply changing to:
import (config.nixpkgs + "/nixos/lib/eval-config.nix") would work, but I'll test a patch to make sure before submitting.