nixos/nix-daemon: fix unknown sandbox warnings

nixos/modules/services/misc/nix-daemon.nix

@@ -11,6 +11,7 @@ let
   nixVersion = getVersion nix;
 
   isNix23 = versionAtLeast nixVersion "2.3pre";
+  isNix24 = versionAtLeast nixVersion "2.4pre";
 
   makeNixBuildUser = nr: {
     name  = "nixbld${toString nr}";
@@ -40,7 +41,11 @@ let
         max-jobs = ${toString (cfg.maxJobs)}
         cores = ${toString (cfg.buildCores)}
         sandbox = ${if (builtins.isBool cfg.useSandbox) then boolToString cfg.useSandbox else cfg.useSandbox}
-        extra-sandbox-paths = ${toString cfg.sandboxPaths}
+
+        ${optionalString (!isNix24) ''
+          extra-sandbox-paths = ${toString cfg.sandboxPaths}
+        ''}
+
         substituters = ${toString cfg.binaryCaches}
         trusted-substituters = ${toString cfg.trustedBinaryCaches}
         trusted-public-keys = ${toString cfg.binaryCachePublicKeys}