To enable debug info for a package that doesn't have it, one might naively expect this work:

  nixpkgs.config.packageOverrides = pkgs: {
    hello = overrideDerivation pkgs.hello (attrs: {
      separateDebugInfo = true;
    });
  };

However, this doesn't work because separateDebugInfo affects mkDerivation, not derivation. So we'd need some way to re-call the original mkDerivation invocation with new arguments.