lightdm: ensure run-directory is /run/lightdm (#46907)

pkgs/applications/display-managers/lightdm/default.nix

@@ -49,6 +49,7 @@ stdenv.mkDerivation rec {
   ] ++ optional withQt4 qt4
     ++ optional withQt5 qtbase;
 
+  patches = [ ./run-dir.patch ];
 
   preConfigure = "NOCONFIGURE=1 ./autogen.sh";
 

pkgs/applications/display-managers/lightdm/run-dir.patch

@@ -0,0 +1,13 @@
+diff --git a/data/lightdm.conf b/data/lightdm.conf
+index 16b80f7..b3af435 100644
+--- a/data/lightdm.conf
++++ b/data/lightdm.conf
+@@ -28,7 +28,7 @@
+ #guest-account-script=guest-account
+ #logind-check-graphical=false
+ #log-directory=/var/log/lightdm
+-#run-directory=/var/run/lightdm
++run-directory=/run/lightdm
+ #cache-directory=/var/cache/lightdm
+ #sessions-directory=/usr/share/lightdm/sessions:/usr/share/xsessions:/usr/share/wayland-sessions
+ #remote-sessions-directory=/usr/share/lightdm/remote-sessions