lib.systems.equals: use lib imports instead of builtins (#507317)

let

  inherit (lib)

    any

    filterAttrs

    attrNames

    filter

    foldl

    hasInfix

    isAttrs

    isFunction

    isList

    mapAttrs

    optional

  */

  equals =

    let

      # perf: avoid lib.isFunction because system attrs are never __functor-style attrsets.

      removeFunctions =

        a: removeAttrs a (builtins.filter (n: builtins.isFunction a.${n}) (builtins.attrNames a));

      # System attrs are never __functor-style attrsets, so builtins.isFunction suffices.

      removeFunctions = a: removeAttrs a (filter (n: builtins.isFunction a.${n}) (attrNames a));

    in

    a: b: removeFunctions a == removeFunctions b;