tuned signature;

--- a/src/Pure/System/options.scala	Sat Mar 11 11:43:47 2023 +0100
+++ b/src/Pure/System/options.scala	Sat Mar 11 11:51:19 2023 +0100
@@ -185,6 +185,8 @@
     opts.foldLeft(Parsers.parse_prefs(options, prefs))(_ + _)
   }
 
+  def init0(): Options = init(prefs = "")
+
 
   /* Isabelle tool wrapper */
 
@@ -430,7 +432,7 @@
   /* preferences */
 
   def make_prefs(
-    defaults: Options = Options.init(prefs = ""),
+    defaults: Options = Options.init0(),
     filter: Options.Entry => Boolean = _ => true
   ): String = {
     (for {
@@ -442,7 +444,7 @@
       .map({ case (x, y, z) => x + " = " + Outer_Syntax.quote_string(y) + z + "\n" }).mkString
   }
 
-  def save_prefs(file: Path = Options.PREFS, defaults: Options = Options.init(prefs = "")): Unit = {
+  def save_prefs(file: Path = Options.PREFS, defaults: Options = Options.init0()): Unit = {
     val prefs = make_prefs(defaults = defaults)
     Isabelle_System.make_directory(file.dir)
     File.write_backup(file, "(* generated by Isabelle " + Date.now() + " *)\n\n" + prefs)

--- a/src/Pure/Tools/build_process.scala	Sat Mar 11 11:43:47 2023 +0100
+++ b/src/Pure/Tools/build_process.scala	Sat Mar 11 11:51:19 2023 +0100
@@ -923,7 +923,7 @@
   final def start_build(): Unit = synchronized_database {
     for (db <- _database) {
       Build_Process.Data.start_build(db, build_uuid, build_context.ml_platform,
-        store.options.make_prefs(Options.init(prefs = ""), filter = _.session_content))
+        store.options.make_prefs(Options.init0(), filter = _.session_content))
     }
   }