disallow aliases in the nixpkgs-tarball eval

[Artturin]

this allows ofborg to still check the aliases.nix file for errors unlike https://github.com/NixOS/ofborg/pull/594 which would have disabled aliases in outpaths.nix

errors in the alias.nix file are caught by outpaths.nix eval so we can disable aliases here

[cole-h]

This doesn't appear to work. pkgs/top-level/release.nix does not take a config argument, but a nixpkgsArgs argument which may contain config. However, even then, this wouldn't work -- these errors don't appear at eval time, but build time.

Compare the following running off of https://github.com/NixOS/nixpkgs/pull/169822:

nix-instantiate  --arg nixpkgs '{ outPath = ./.; revCount = 1; shortRev = "73382eb"; rev = "73382ebb720506d43dd0ef031d5cb19a1b96f678"; }' --arg nixpkgsArgs '{ config = { allowAliases = false; }; }' ./pkgs/top-level/release.nix -A tarball
# succeeds

and

nix-build --arg nixpkgs '{ outPath = ./.; revCount = 1; shortRev = "73382eb"; rev = "73382ebb720506d43dd0ef031d5cb19a1b96f678"; }' --arg nixpkgsArgs '{ config = { allowAliases = false; }; }' ./pkgs/top-level/release.nix -A tarball
# fails due to alias

[cole-h]

Reverted in #598.

This may be helpful -- the error during build comes after the following:

++ nix-env -f /nix/store/7haipzvw641rgsfak0w9g57xy6nj9qb8-master --show-trace --argstr system x86_64-linux --arg config '{ allowAliases = false; }' --option experimental-features no-url-literals -qa --drv-path --system-filter '*' --system --option build-users-group ''                                                                                    
error: undefined variable 'dateutil'                                                                                                                                            

So maybe the necessary change is above in the list-packages-no-aliases step (roughly line 451)?