src/Pure/Tools/build.scala

   {
     def output_path: Option[Path] = if (do_output) Some(output) else None
 
     private val parent = info.parent.getOrElse("")
 
-    private val args_file = File.tmp_file("args")
+    private val args_file = Isabelle_System.tmp_file("args")
     File.write(args_file, YXML.string_of_body(
       if (is_pure(name)) Options.encode(info.options)
       else
         {
           import XML.Encode._