Describe the bug

When using nix run, the command does not use the nixConfig options declared in the flake.nix. nix build does read it accordingly.

For example when using nixConfig.extra-substituters with nix run the build process won't use the binary cache, but when using nix build it does.

Steps To Reproduce

1. Execute nix run github:AmitHalpert/contamination
2. ^ binary cache is not used ^
3. Execute nix run github:AmitHalpert/contamination \ --option extra-substituters 'https://contamination.cachix.org/' \ --option extra-trusted-public-keys 'contamination.cachix.org-1:KmdW5xVF8ccKEb9tvK6qtEMW+lGa83seGgFyBOkeM/4='
4. ^ binary is being used ^
5. Execute nix build github:AmitHalpert/contamination (binary cache is used and the options are prompted when running)

Expected behavior
When executing nix run on a flake with the nixConfig options set I expect nix run to read those options and use them accordingly.

nix-env --version output
nix-env (Nix) 2.7.0pre20220127_558c4ee