overlays: move fcitx5-table-extra patch to top-level

nix/configurations/vanadium.nix

@@ -49,6 +49,7 @@ in
             ../overlays/nix-tree.nix
             ../overlays/wallpapers.nix
             ../overlays/nil.nix
+            ../overlays/fcitx5-table-extra-taiwanese.nix
 
             ../overlays/iosevka.nix
             ../packages/overlay.nix

nix/configurations/vanadium/overlay.nix

@@ -47,15 +47,4 @@ in
       ./patches/fcitx5-chinese-addons/disable-fullwidth.patch
       # Note: disabling pinyin helper breaks canjie
     ];
-    fcitx5-table-extra.__output.src = _: final.fetchFromGitHub {
-      owner = "leana8959";
-      repo = "fcitx5-table-extra";
-      rev = "3fb844280a5154389be17e422a98ad89cafccc38";
-      hash = "sha256-8iGNQYQH8tT3p6VedVBgfxHqXVLkFEiDEd1H7CBFXqg=";
-      fetchSubmodules = true;
-    };
-    fcitx5-table-extra.__output.nativeBuildInputs.__append = [ final.python3 ];
-    fcitx5-table-extra.__output.preConfigure.__prepend = ''
-      python3 ./generate.py
-    '';
   })

nix/overlays/fcitx5-table-extra-taiwanese.nix

@@ -0,0 +1,18 @@
+let
+  sources = import ../sources.nix;
+in
+  final: prev: {
+    fcitx5-table-extra = prev.fcitx5-table-extra.overrideAttrs (oldAttrs: {
+      src = sources.fcitx5-table-extra;
+      nativeBuildInputs =
+        oldAttrs.nativeBuildInputs or []
+        ++ [
+          final.python3
+        ];
+      preConfigure =
+        oldAttrs.preConfigure or ""
+        + ''
+          python3 ./generate.py
+        '';
+    });
+  }