Repro for NixOS/nixpkgs#86775

To reproduce:

• Make foo unreadable (chmod a-r foo)

• Try to enter a nix shell (nix-shell)

• Observe that the command fails because it is unable to read foo (error: opening file '/home/j/projects/bugs/nix-greedy-source/foo': Permission denied)

• Modify nixpkgs thusly:

  diff --git a/pkgs/development/haskell-modules/make-package-set.nix b/pkgs/development/haskell-modules/make-package-set.nix
  index 45fe475b733..38265a2e8af 100644
  --- a/pkgs/development/haskell-modules/make-package-set.nix
  +++ b/pkgs/development/haskell-modules/make-package-set.nix
  @@ -354,7 +354,7 @@ in package-set { inherit pkgs stdenv callPackage; } self // {
           #
           #   isNotSelected lens [ frontend backend common ]
           #   => true
  -        isNotSelected = input: pkgs.lib.all (p: input.outPath or null != p.outPath) selected;
  +        isNotSelected = input: true;
  
           # A function that takes a list of list of derivations, filters out all
           # the `selected` packages from each list, and concats the results.

• Try to enter a nix shell (nix-shell)

• Observe that only package.yaml is read and you can enter the shell successfully