Log to nullOutputStream() instead of hijacking System.out by default

src/main/java/org/apache/harmony/unpack200/Archive.java

@@ -148,7 +148,7 @@ public class Archive {
                     segment.setLogLevel(logLevel);
                     segment
                             .setLogStream(logFile != null ? (OutputStream) logFile
-                                    : (OutputStream) System.out);
+                                    : OutputStream.nullOutputStream());
                     segment.setPreRead(false);
 
                     if (i == 1) {