fcron: do not chmod at all

fcron does handle permissions on its own correctly

nixos/modules/services/scheduling/fcron.nix

@@ -143,10 +143,12 @@ in
       };
 
       preStart = ''
-        ${pkgs.coreutils}/bin/mkdir -m 0770 -p /var/spool/fcron
-        ${pkgs.coreutils}/bin/chown -R fcron:fcron /var/spool/fcron
+        install \
+          --mode 0770 \
+          --owner fcron \
+          --group fcron \
+          --directory /var/spool/fcron
         # load system crontab file
-        set -x
         #${pkgs.fcron}/bin/fcrontab -u systab ${pkgs.writeText "systab" cfg.systab}
       '';