hotfix: exported overlays incompatible with emacs-overlay

[montchr]

depends on #468
attempts to address #464

this probably is not the way to go in the long run. personally, i don't use the exported overlays, but i do use emacs-overlay – as numerous people have noted in #464, recent changes to emacs-overlay are incompatible with the way exportOverlays works.

[a12l]

It seems that my problem with emacs-overlay isn't solved with this fix.

$ nix flake update
warning: updating lock file '/home/a12l/Long-Term/NixCFG/flake.lock':
[...]
• Updated input 'digga':
    'github:divnix/digga/29bbac0173859812893d777fdce204af83a231ea' (2022-05-16)
  → 'github:divnix/digga/6b0c0aa1ae0410960de8f3ae7168e1991783ecbb' (2022-05-21)
• Updated input 'emacs-overlay':
    'github:nix-community/emacs-overlay/334ba8c610cf5e41dfe130507030e5587e3551b4' (2022-05-09)
  → 'github:nix-community/emacs-overlay/7a5353c3d27749912df89d1083e9b675f70accb4' (2022-05-26)
• Added input 'emacs-overlay/flake-utils':
    'github:numtide/flake-utils/04c1b180862888302ddfb2e3ad9eaa63afc60cf8' (2022-05-17)
• Added input 'emacs-overlay/nixpkgs':
    follows 'nixpkgs'
direnv: loading ~/Long-Term/NixCFG/.envrc
direnv: using flake
error: value is null while a set was expected

       at /nix/store/wn1xry1ra2qmj74nl5idlgz7y4vhrq66-source/default.nix:180:6:

          179|
          180| } // super.lib.optionalAttrs (super.config.allowAliases or true) {
             |      ^
          181|   emacsGcc = builtins.trace "emacsGcc has been renamed to emacsNativeComp, please update your expression." emacsNativeComp;
(use '--show-trace' to show detailed location information)
direnv: nix-direnv: renewed cache
direnv: export ~XDG_DATA_DIRS

[GTrunSec]

Can be sure the problem is here：https://github.com/divnix/digga/blob/main/src/mkFlake/fup-adapter.nix#L44

[montchr]

Closing in favor of #483