tv cgit,sanitize: use empty directory from store

This is required for deploying to machines without /var/empty, like the
nixos-install chroot.

modules/tv/git/cgit.nix

@@ -14,7 +14,7 @@ in
     name = "fcgiwrap";
     uid = 2851179180; # genid fcgiwrap
     group = "fcgiwrap";
-    home = "/var/empty";
+    home = toString (pkgs.runCommand "empty" {} "mkdir -p $out");
   };
 
   users.extraGroups = lib.singleton {

modules/tv/sanitize.nix

@@ -3,6 +3,6 @@
 {
   nixpkgs.config.packageOverrides = pkgs:
     {
-      nano = /var/empty;
+      nano = pkgs.runCommand "empty" {} "mkdir -p $out";
     };
 }