diff -r bdf6933f7ac9 -r c61acb4855b6 src/Pure/Tools/build.scala
--- 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