[FIXED JENKINS-19473] Trying to work around jzlib bug.

core/src/main/java/hudson/FilePath.java

@@ -632,7 +632,12 @@ public final class FilePath implements Serializable {
                 }
             }
             public OutputStream compress(OutputStream out) throws IOException {
-                return new GZIPOutputStream(new BufferedOutputStream(out));
+                return new GZIPOutputStream(new BufferedOutputStream(out),
+                        // TODO JENKINS-19473 workaround; replace when jzlib fixed
+                        new com.jcraft.jzlib.Deflater(6, 15+16, 9),   // use 9 for memLevel
+                        512,
+                        true
+                );
             }
         };