nixos/networkd: fix range assertions on 32 bit Nix

nixos/modules/system/boot/systemd-lib.nix

@@ -73,11 +73,19 @@ in rec {
     optional (attr ? ${name} && !(min <= attr.${name} && max >= attr.${name}))
       "Systemd ${group} field `${name}' is outside the range [${toString min},${toString max}]";
 
+  assertMinimum = name: min: group: attr:
+    optional (attr ? ${name} && attr.${name} < min)
+      "Systemd ${group} field `${name}' must be greater than or equal to ${toString min}";
+
   assertOnlyFields = fields: group: attr:
     let badFields = filter (name: ! elem name fields) (attrNames attr); in
     optional (badFields != [ ])
       "Systemd ${group} has extra fields [${concatStringsSep " " badFields}].";
 
+  assertInt = name: group: attr:
+    optional (attr ? ${name} && !isInt attr.${name})
+      "Systemd ${group} field `${name}' is not an integer";
+
   checkUnitConfig = group: checks: attrs: let
     # We're applied at the top-level type (attrsOf unitOption), so the actual
     # unit options might contain attributes from mkOverride that we need to