src/Pure/Tools/build.scala

     override def echo(msg: String) { Console.println(msg) }
     override def theory(session: String, theory: String): Unit =
       if (verbose) echo(session + ": theory " + theory)
 
     @volatile private var is_stopped = false
-    def interrupt_handler[A](e: => A): A = Interrupt.handler { is_stopped = true } { e }
+    def interrupt_handler[A](e: => A): A = POSIX_Interrupt.handler { is_stopped = true } { e }
     override def stopped: Boolean =
     {
       if (Thread.interrupted) is_stopped = true
       is_stopped
     }