nixos/system-path: don't link /etc/xdg/ uncoditionally (#530382)

doc/release-notes/rl-2611.section.md

@@ -10,6 +10,7 @@
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
+- Paths under `/etc/xdg/` from packages in `environment.systemPackages` are no longer linked into the global `/etc/` by default. Modules depending on such directories must declare them explicitly using `environment.pathsToLink`.
 - `databricks-cli` has been updated from `0.290.2` to `1.x.x`, the first major release. OAuth tokens for interactive logins (`auth_type = databricks-cli`) are now stored in the OS-native secure store by default (Secret Service on Linux) instead of `~/.databricks/token-cache.json`; cached tokens from older versions are not migrated, so run `databricks auth login` once per profile after upgrading. To keep the previous file-backed storage, set `DATABRICKS_AUTH_STORAGE=plaintext` or add `auth_storage = plaintext` under `[__settings__]` in `~/.databrickscfg`. Additionally, the `vector_search_endpoints` DABs resource renamed `min_qps` to `target_qps` (and the `vector-search-endpoints` command renamed `--min-qps` to `--target-qps`). See the [upstream changelog](https://github.com/databricks/cli/blob/main/CHANGELOG.md) for details.
 
 - `hurl` has been updated to `8.x.x` which has some breaking changes. See [upstream changelog](https://github.com/Orange-OpenSource/hurl/releases/tag/8.0.0) for details.

nixos/modules/config/system-path.nix

@@ -187,7 +187,6 @@ in
 
     environment.pathsToLink = [
       "/bin"
-      "/etc/xdg"
       "/etc/gtk-2.0"
       "/etc/gtk-3.0"
       "/lib" # FIXME: remove and update debug-info.nix

nixos/modules/config/xdg/autostart.nix

@@ -22,8 +22,6 @@
   };
 
   config = {
-    # FIXME this does not actually work because "/etc/xdg" is linked
-    # unconditionally in `nixos/modules/config/system-path.nix`
     environment.pathsToLink = lib.mkIf config.xdg.autostart.install [
       "/etc/xdg/autostart"
     ];