add flush are println in DefaultHandlerHandler#handleInput

- some java jvms do not flush the output for System.err.println()
in particular z/OS
PR:  26655
Obtained from: wwalsh at curamsoftware dot com


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@276015 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/input/DefaultInputHandler.java

@@ -53,6 +53,7 @@ public class DefaultInputHandler implements InputHandler {
                 new DataInputStream(new KeepAliveInputStream(getInputStream()));
             do {
                 System.err.println(prompt);
+                System.err.flush();
                 try {
                     String input = in.readLine();
                     request.setInput(input);