prefer strict test of system options;

--- a/src/Pure/System/registry.scala	Sat Nov 11 20:43:20 2023 +0100
+++ b/src/Pure/System/registry.scala	Sat Nov 11 21:05:41 2023 +0100
@@ -34,7 +34,7 @@
 
   object Host extends Table[List[Options.Spec]]("host") {
     def options_spec(a: TOML.Key, b: TOML.T): Option[Options.Spec] =
-      TOML.Scalar.unapply(b).map(Options.Spec.eq(a, _, permissive = true))
+      TOML.Scalar.unapply(b).map(Options.Spec.eq(a, _))
 
     override def table_value(a: String, t: TOML.Table): List[Options.Spec] =
       for ((a, b) <- t.any.values; s <- options_spec(a, b)) yield s