extract console redirection stuff from "quit" function

so we can use it for scripts that don't reboot at their end

modules/s6/default.nix

@@ -94,10 +94,13 @@ let
     };
     ".s6-svscan" =
       let
-        quit = message: ''
+        openConsole = ''
           #!${execline}/bin/execlineb -P
           ${execline}/bin/redirfd -w 2 /dev/console
           ${execline}/bin/fdmove -c 1 2
+        '';
+        quit = message: ''
+          ${openConsole}
           ${execline}/bin/foreground { ${s6-linux-init}/bin/s6-linux-init-echo -- ${message} }
           ${s6-linux-init}/bin/s6-linux-init-hpr -fr
         '';