tuned signature;

--- a/src/Pure/System/options.scala	Tue Mar 13 18:28:12 2018 +0100
+++ b/src/Pure/System/options.scala	Tue Mar 13 18:40:25 2018 +0100
@@ -130,14 +130,14 @@
   def read_prefs(file: Path = PREFS): String =
     if (file.is_file) File.read(file) else ""
 
-  def init(prefs: String = read_prefs(PREFS)): Options =
+  def init(prefs: String = read_prefs(PREFS), opts: List[String] = Nil): Options =
   {
     var options = empty
     for {
       dir <- Isabelle_System.components()
       file = dir + OPTIONS if file.is_file
     } { options = Parser.parse_file(options, file.implode, File.read(file)) }
-    Options.Parser.parse_prefs(options, prefs)
+    (Options.Parser.parse_prefs(options, prefs) /: opts)(_ + _)
   }
 
 

--- a/src/Pure/Tools/build.scala	Tue Mar 13 18:28:12 2018 +0100
+++ b/src/Pure/Tools/build.scala	Tue Mar 13 18:40:25 2018 +0100
@@ -699,7 +699,7 @@
     var check_keywords: Set[String] = Set.empty
     var list_files = false
     var no_build = false
-    var options = (Options.init() /: build_options)(_ + _)
+    var options = Options.init(opts = build_options)
     var system_mode = false
     var verbose = false
     var exclude_sessions: List[String] = Nil