webpack requires webpack-cli and vice-versa

[epigramengineer]

Describe the bug
Given webpack and webpack-cli installed from a synced unstable channel or stable (20.09) both claim to require the other to function.

To Reproduce

• Install nodePackages.webpack and nodePackages.webpack-cli from unstable channel. My exact pinned version with niv:

❯ niv show unstable
unstable
  homepage: 
  url: https://github.com/NixOS/nixpkgs/archive/f0efbe21f9ae1e17d1aca922708f1bdef605039d.tar.gz
  owner: NixOS
  branch: nixpkgs-unstable
  url_template: https://github.com/<owner>/<repo>/archive/<rev>.tar.gz
  repo: nixpkgs
  type: tarball
  sha256: 0d3xyihm9f7x43vbrs1hi2fxchqi7b5jrwvvc7swhjvva1cyax1n
  description: Nix Packages collection
  rev: f0efbe21f9ae1e17d1aca922708f1bdef605039d

Expected behavior
webpack and webpack-cli to function correctly

Screenshots
If applicable, add screenshots to help explain your problem.

❯ webpack --version
CLI for webpack must be installed.
  webpack-cli (https://github.com/webpack/webpack-cli)

We will use "yarn" to install the CLI via "yarn add -D webpack-cli".
Do you want to install 'webpack-cli' (yes/no): no
You need to install 'webpack-cli' to use webpack via CLI.
You can also install the CLI manually.
❯ webpack-cli --version
[webpack-cli] It looks like webpack is not installed.
✔ Would you like to install 'webpack' package? (That will run 'yarn add -D webpack') (Y/n) · false

Additional context

• This appears to be the same as webpack CLI requires webpack-cli #42275 Not sure if I should re-open that one instead. If so apologies..

Notify maintainers
@dywedir

Metadata
Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

❯ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.4.108, NixOS, 20.09.3719.0c7f43d5917 (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.10`
 - channels($user): `"nixos-20.09-20.09.2290.647cc06986c"`
 - channels(root): `"nixos-20.09.3719.0c7f43d5917, nixos-unstable-21.05pre279456.04a2b269d89"`
 - nixpkgs: `/nix/store/2ak8av2kbi3cdj1mf5sp9b96y4qr4vyh-unstable-src`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: nodePackages.webpack nodePackages.webpack-cli
# a list of nixos modules affected by the problem
module:

[FliegendeWurst]

This appears to be the same as #42275 Not sure if I should re-open that one instead. If so apologies..

Yes, this issue is the same as #42275