Use IO.Newline for stack trace

internal/util-logging/src/main/scala/sbt/internal/util/StackTrace.scala

@@ -3,6 +3,9 @@
  */
 package sbt.internal.util
 
+import sbt.io.IO
+import scala.collection.mutable.ListBuffer
+
 object StackTrace {
   def isSbtClass(name: String) = name.startsWith("sbt.") || name.startsWith("xsbt.")
 
@@ -18,9 +21,9 @@ object StackTrace {
    *   where the line for the Throwable is counted plus one line for each stack element.
    *   Less lines will be included if there are not enough stack elements.
    */
-  def trimmed(t: Throwable, d: Int): String = {
+  def trimmedLines(t: Throwable, d: Int): List[String] = {
     require(d >= 0)
-    val b = new StringBuilder()
+    val b = new ListBuffer[String]()
 
     def appendStackTrace(t: Throwable, first: Boolean): Unit = {
 
@@ -33,16 +36,12 @@ object StackTrace {
         }
 
       def appendElement(e: StackTraceElement): Unit = {
-        b.append("\tat ")
-        b.append(e)
-        b.append('\n')
+        b.append("\tat " + e)
         ()
       }
 
-      if (!first)
-        b.append("Caused by: ")
-      b.append(t)
-      b.append('\n')
+      if (!first) b.append("Caused by: " + t.toString)
+      else b.append(t.toString)
 
       val els = t.getStackTrace()
       var i = 0
@@ -59,7 +58,21 @@ object StackTrace {
       c = c.getCause()
       appendStackTrace(c, false)
     }
-    b.toString()
+    b.toList
   }
 
+  /**
+   * Return a printable representation of the stack trace associated
+   * with t.  Information about t and its Throwable causes is included.
+   * The number of lines to be included for each Throwable is configured
+   * via d which should be greater than or equal to 0.
+   *
+   * - If d is 0, then all elements are included up to (but not including)
+   *   the first element that comes from sbt.
+   * - If d is greater than 0, then up to that many lines are included,
+   *   where the line for the Throwable is counted plus one line for each stack element.
+   *   Less lines will be included if there are not enough stack elements.
+   */
+  def trimmed(t: Throwable, d: Int): String =
+    trimmedLines(t, d).mkString(IO.Newline)
 }