Merge pull request #7278 from nbp/nixos-manual-x86

Fix NixOS Manual builds

nixos/modules/misc/nixpkgs.nix

···
     };
 
     nixpkgs.system = mkOption {
-      type = types.str;
-      default = builtins.currentSystem;
+      type = types.uniq types.str;
+      example = "i686-linux";
       description = ''
         Specifies the Nix platform type for which NixOS should be built.
         If unset, it defaults to the platform type of your host system.

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

···
   versionModule =
     { system.nixosVersionSuffix = config.system.nixosVersionSuffix;
       system.nixosRevision = config.system.nixosRevision;
+      nixpkgs.system = config.nixpkgs.system;
     };
 
   eval = evalModules {

nixos/modules/services/networking/btsync.nix

···
 
       package = mkOption {
         type = types.package;
-        default = pkgs.bittorrentSync14;
         example = literalExample "pkgs.bittorrentSync20";
         description = ''
           Branch of bittorrent sync to use.
···
           message   = "If you're using an API key, you must enable the web server.";
         }
       ];
+
+    services.btsync.package = mkOptionDefault pkgs.bittorrentSync14;
 
     users.extraUsers.btsync = {
       description     = "Bittorrent Sync Service user";