nixos/lightdm: use systemd.tmpfiles (#46734)

This also makes logs appear at /var/log/lightdm

(cherry picked from commit 67e9571)

nixos/modules/services/x11/display-managers/lightdm.nix

@@ -197,7 +197,7 @@ in
       # lightdm relaunches itself via just `lightdm`, so needs to be on the PATH
       execCmd = ''
         export PATH=${lightdm}/sbin:$PATH
-        exec ${lightdm}/sbin/lightdm --log-dir=/var/log --run-dir=/run
+        exec ${lightdm}/sbin/lightdm
       '';
     };
 
@@ -246,12 +246,19 @@ in
     '';
 
     users.users.lightdm = {
-      createHome = true;
-      home = "/var/lib/lightdm-data";
+      home = "/var/lib/lightdm";
       group = "lightdm";
       uid = config.ids.uids.lightdm;
     };
 
+    systemd.tmpfiles.rules = [
+      "d /var/run/lightdm 0711 lightdm lightdm 0"
+      "d /var/cache/lightdm 0711 root lightdm -"
+      "d /var/lib/lightdm 1770 lightdm lightdm -"
+      "d /var/lib/lightdm-data 1775 lightdm lightdm -"
+      "d /var/log/lightdm 0711 root lightdm -"
+    ];
+
     users.groups.lightdm.gid = config.ids.gids.lightdm;
     services.xserver.tty     = null; # We might start multiple X servers so let the tty increment themselves..
     services.xserver.display = null; # We specify our own display (and logfile) in xserver-wrapper up there