proper prover_options for batch-build;

--- a/src/Pure/System/options.scala	Thu Aug 12 13:13:10 2021 +0200
+++ b/src/Pure/System/options.scala	Thu Aug 12 13:14:49 2021 +0200
@@ -141,11 +141,6 @@
   }
 
 
-  /* encode */
-
-  val encode: XML.Encode.T[Options] = (options => options.encode)
-
-
   /* Isabelle tool wrapper */
 
   val isabelle_tool = Isabelle_Tool("options", "print Isabelle system options",

--- a/src/Pure/Tools/build_job.scala	Thu Aug 12 13:13:10 2021 +0200
+++ b/src/Pure/Tools/build_job.scala	Thu Aug 12 13:14:49 2021 +0200
@@ -427,11 +427,13 @@
           Exn.capture { process.await_startup() } match {
             case Exn.Res(_) =>
               val resources_yxml = resources.init_session_yxml
+              val encode_options: XML.Encode.T[Options] =
+                options => session.prover_options(options).encode
               val args_yxml =
                 YXML.string_of_body(
                   {
                     import XML.Encode._
-                    pair(string, list(pair(Options.encode, list(pair(string, properties)))))(
+                    pair(string, list(pair(encode_options, list(pair(string, properties)))))(
                       (session_name, info.theories))
                   })
               session.protocol_command("build_session", resources_yxml, args_yxml)