Without the change the eval fails as:

    $ nix-instantiate -A minimal-bootstrap.bash --argstr system i686-linux
    error:
       … while calling the 'derivationStrict' builtin
         at <nix/derivation-internal.nix>:37:12:
           36|
           37|   strict = derivationStrict drvAttrs;
             |            ^
           38|

       … while evaluating derivation 'bash-5.2.15'
         whose name attribute is located at pkgs/os-specific/linux/minimal-bootstrap/bash/2.nix:85:19

       … while evaluating attribute 'PATH' of derivation 'bash-5.2.15'
         at pkgs/os-specific/linux/minimal-bootstrap/bash/2.nix:108:11:
          107|           SHELL = "${bash_2_05}/bin/bash";
          108|           PATH = lib.makeBinPath (
             |           ^
          109|             (env.nativeBuildInputs or [ ])

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: function 'anonymous lambda' called without required argument 'rewriteURL'
       at /tmp/nixpkgs/pkgs/build-support/fetchurl/boot.nix:5:1:
            4|
            5| {
             | ^
            6|   rewriteURL,