zigbee2mqtt: make systemd support optional

pkgs/servers/zigbee2mqtt/default.nix

···
 { lib
+, stdenv
 , buildNpmPackage
 , fetchFromGitHub
 , systemdMinimal
 , nixosTests
 , nix-update-script
+, withSystemd ? lib.meta.availableOn stdenv.hostPlatform systemdMinimal
 }:
 
 buildNpmPackage rec {
···
 
   npmDepsHash = "sha256-AjCeRU/Ew9UquqGPuJeGRC48kCi9uRZaI5Bam365Wwk=";
 
-  buildInputs = [
+  buildInputs = lib.optionals withSystemd [
     systemdMinimal
   ];
 
+  npmFlags = lib.optionals (!withSystemd) [ "--omit=optional" ];
+
   passthru.tests.zigbee2mqtt = nixosTests.zigbee2mqtt;
   passthru.updateScript = nix-update-script { };
 
···
       In this way you can integrate your Zigbee devices with whatever smart home infrastructure you are using.
     '';
     maintainers = with maintainers; [ sweber hexa ];
-    platforms = platforms.linux;
     mainProgram = "zigbee2mqtt";
   };
 }