neovim-unwrapped: enable treesitter tests

The full `functionaltest` fails for various reasons. 
We dont have to run all of it but we can try enabling some of it,
starting with the treesitter tests.
Right now removing the treesitter parsers trigger no error so it's easy
to either not see an error in their installation of a version mismatch.
Running the tests should help mitigate this shortcoming.

pkgs/by-name/ne/neovim-unwrapped/package.nix

@@ -19,6 +19,7 @@
   procps ? null,
   versionCheckHook,
   nix-update-script,
+  writableTmpDirAsHomeHook,
 
   # now defaults to false because some tests can be flaky (clipboard etc), see
   # also: https://github.com/neovim/neovim/issues/16233
@@ -161,22 +162,18 @@ stdenv.mkDerivation (
       unibilium
       utf8proc
     ]
-    ++ lib.optionals finalAttrs.finalPackage.doCheck [
-      glibcLocales
-      procps
-    ]
     ++ lib.optionals (stdenv.hostPlatform.libc != "glibc") [
       # Provide libintl for non-glibc platforms
       gettext
     ];
 
-    doCheck = false;
+    doCheck = true;
 
     # to be exhaustive, one could run
     # make oldtests too
     checkPhase = ''
       runHook preCheck
-      make functionaltest
+      make functionaltest__treesitter
       runHook postCheck
     '';
 
@@ -219,6 +216,7 @@ stdenv.mkDerivation (
       # third-party/CMakeLists.txt is not read at all.
       (lib.cmakeBool "USE_BUNDLED" false)
       (lib.cmakeBool "ENABLE_TRANSLATIONS" true)
+      (lib.cmakeBool "USE_BUNDLED_BUSTED" false)
     ]
     ++ (
       if lua.pkgs.isLuaJIT then
@@ -252,6 +250,12 @@ stdenv.mkDerivation (
 
     nativeInstallCheckInputs = [
       versionCheckHook
+      lua.pkgs.busted
+      writableTmpDirAsHomeHook
+      glibcLocales
+
+      # needs git for vim.pack tests as well
+      procps
     ];
     versionCheckProgram = "${placeholder "out"}/bin/nvim";
     doInstallCheck = true;