handle absence of CONT signal

util/collection/Signal.scala

@@ -2,7 +2,9 @@ package sbt
 
 object Signals
 {
-	def withHandler[T](handler: () => Unit, signal: String = "INT")(action: () => T): T =
+	val CONT = "CONT"
+	val INT = "INT"
+	def withHandler[T](handler: () => Unit, signal: String = INT)(action: () => T): T =
 	{
 		val result = 
 			try
@@ -17,6 +19,13 @@ object Signals
 			case Right(v) => v
 		}
 	}
+	def supported(signal: String): Boolean =
+		try
+		{
+			val signals = new Signals0
+			signals.supported(signal)
+		}
+		catch { case e: LinkageError => false }
 }
 
 // Must only be referenced using a
@@ -24,6 +33,13 @@ object Signals
 // block to 
 private final class Signals0
 {
+	def supported(signal: String): Boolean =
+	{
+			import sun.misc.Signal
+		try { new Signal(signal); true }
+		catch { case e: IllegalArgumentException => false }
+	}
+
 	// returns a LinkageError in `action` as Left(t) in order to avoid it being
 	// incorrectly swallowed as missing Signal/SignalHandler
 	def withHandler[T](signal: String, handler: () => Unit, action: () => T): Either[Throwable, T] =

util/complete/LineReader.scala

@@ -35,7 +35,7 @@ abstract class JLine extends LineReader
 
 	private[this] def readLineDirect(prompt: String, mask: Option[Char]): String =
 		if(handleCONT)
-			Signals.withHandler(() => resume(), signal = "CONT")( () => readLineDirectRaw(prompt, mask) )
+			Signals.withHandler(() => resume(), signal = Signals.CONT)( () => readLineDirectRaw(prompt, mask) )
 		else
 			readLineDirectRaw(prompt, mask)
 	private[this] def readLineDirectRaw(prompt: String, mask: Option[Char]): String =
@@ -90,7 +90,7 @@ private object JLine
 
 	def simple(historyPath: Option[File], handleCONT: Boolean = HandleCONT): SimpleReader = new SimpleReader(historyPath, handleCONT)
 	val MaxHistorySize = 500
-	val HandleCONT = !java.lang.Boolean.getBoolean("sbt.disable.cont")
+	val HandleCONT = !java.lang.Boolean.getBoolean("sbt.disable.cont") && Signals.supported(Signals.CONT)
 }
 
 trait LineReader