[Backport release-26.05] nixos/hydra: Add zstd and bzip2 to hydra-server's PATH (#549815)

nixos/modules/services/continuous-integration/hydra/default.nix

@@ -398,6 +398,11 @@ in
       wantedBy = [ "multi-user.target" ];
       requires = [ "hydra-init.service" ];
       after = [ "hydra-init.service" ];
+      path = [
+        # these are used to serve logs if they are compressed with zstd or bzip2
+        pkgs.zstd
+        pkgs.bzip2
+      ];
       environment = serverEnv // {
         HYDRA_DBI = "${serverEnv.HYDRA_DBI};application_name=hydra-server";
       };