update-scripts: move out of flake

See the explanation in the new update-scripts/README.md file.

update-scripts/efmls-configs.nix

@@ -0,0 +1,54 @@
+{
+  lib,
+  vimPlugins,
+  writeText,
+}:
+let
+  tools = lib.trivial.importJSON "${vimPlugins.efmls-configs-nvim.src}/doc/supported-list.json";
+  languages = lib.attrNames tools;
+
+  toLangTools' = lang: kind: lib.map (lib.getAttr "name") (tools.${lang}.${kind} or [ ]);
+
+  miscLinters = toLangTools' "misc" "linters";
+  miscFormatters = toLangTools' "misc" "formatters";
+
+  sources =
+    (lib.listToAttrs (
+      lib.map (
+        lang:
+        let
+          toLangTools = toLangTools' lang;
+        in
+        {
+          name = lang;
+          value = {
+            linter = {
+              inherit lang;
+              possible = (toLangTools "linters") ++ miscLinters;
+            };
+            formatter = {
+              inherit lang;
+              possible = (toLangTools "formatters") ++ miscFormatters;
+            };
+          };
+        }
+      ) languages
+    ))
+    // {
+      all = {
+        linter = {
+          lang = "all languages";
+          possible = miscLinters;
+        };
+        formatter = {
+          lang = "all languages";
+          possible = miscFormatters;
+        };
+      };
+    };
+in
+writeText "efmls-configs-sources.nix" (
+  "# WARNING: DO NOT EDIT\n"
+  + "# This file is generated with packages.<system>.efmls-configs-sources, which is run automatically by CI\n"
+  + (lib.generators.toPretty { } sources)
+)