nagios: enable darwin support

nixos/tests/all-tests.nix

···
   mysql-backup = handleTest ./mysql/mysql-backup.nix {};
   mysql-replication = handleTest ./mysql/mysql-replication.nix {};
   n8n = handleTest ./n8n.nix {};
-  nagios = handleTest ./nagios.nix {};
+  nagios = handleTestOn [ "x86_64-linux" "aarch64-linux" ] ./nagios.nix {};
   nar-serve = handleTest ./nar-serve.nix {};
   nat.firewall = handleTest ./nat.nix { withFirewall = true; };
   nat.standalone = handleTest ./nat.nix { withFirewall = false; };

pkgs/servers/monitoring/nagios/default.nix

···
     homepage = "https://www.nagios.org/";
     changelog = "https://github.com/NagiosEnterprises/nagioscore/blob/nagios-${finalAttrs.version}/Changelog";
     license = lib.licenses.gpl2;
-    platforms = lib.platforms.linux;
+    platforms = lib.platforms.unix;
     mainProgram = "nagios";
     maintainers = with lib.maintainers; [ immae thoughtpolice relrod anthonyroussel ];
   };