proper dynamic access (amending c3f07c950116);

--- a/src/Pure/General/logger.scala	Tue Mar 05 16:20:40 2024 +0100
+++ b/src/Pure/General/logger.scala	Tue Mar 05 16:22:24 2024 +0100
@@ -20,7 +20,7 @@
         if (progress != null) progress.echo(msg)
     }
 
-  def make_system_log(progress: Progress, options: Options, guard_time: Time = Time.min): Logger =
+  def make_system_log(progress: => Progress, options: Options, guard_time: Time = Time.min): Logger =
     options.string("system_log") match {
       case "" => new Logger
       case "-" => make_progress(progress, guard_time = guard_time)