Fix warnAlias mangling attrsets

[keysmashes]

This fixes an issue introduced in #456527.

Before:

$ nix-instantiate --eval --expr 'with import ./. {}; pkgs.hostPlatform.isLinux'
trace: evaluation warning: 'hostPlatform' has been renamed to/replaced by 'stdenv.hostPlatform'
error: attempt to call something which is not a function but a string: "isLinux"
       at «string»:1:39:
            1| with import ./. {}; pkgs.hostPlatform.isLinux
             |                                       ^

After:

$ nix-instantiate --eval --expr 'with import ./. {}; pkgs.hostPlatform.isLinux'
trace: evaluation warning: 'hostPlatform' has been renamed to/replaced by 'stdenv.hostPlatform'
true

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[trofi]

Also fixes nix eval --impure --expr 'with import ./. {}; buildPlatform.aesSupport' for me. Thank you!

[emilazy]

Thanks. Sorry for missing this.

[emilazy]

Could you add an “aliases:” prefix to the commit message? (Sorry for missing that too…)

[keysmashes]

done!

[emilazy]

Thanks!