flake: move documentation building from CI to flake check

.github/workflows/check.yml

@@ -21,4 +21,3 @@ jobs:
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
       - run: nix flake check --all-systems --builders ""
       - run: nix flake check --all-systems --builders "" ./templates/_wrapper/simple --no-write-lock-file
-      - run: nix build .#docs --show-trace --builders ""

flake-modules/checks.nix

@@ -1,11 +1,13 @@
 {
   perSystem = {
     pkgs,
+    config,
     makeNixvimWithModuleUnfree,
     makeNixvimWithModule,
     ...
   }: {
-    checks = {
+    checks =
+      {
         tests = import ../tests {
           inherit pkgs;
           inherit (pkgs) lib;
@@ -26,6 +28,11 @@
           inherit pkgs;
           inherit (pkgs) lib;
         };
-    };
+      }
+      # Do not check if documentation builds fine on darwin as it fails:
+      # > sandbox-exec: pattern serialization length 69298 exceeds maximum (65535)
+      // (pkgs.lib.optionalAttrs (!pkgs.stdenv.isDarwin) {
+        inherit (config.packages) docs;
+      });
   };
 }