[FIXED HUDSON-4039] Fixed a serilization problem.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@19883 71c3de6d-444a-0410-be80-ed276b4c234a

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

@@ -1514,7 +1514,7 @@ public final class FilePath implements Serializable {
         private static final long serialVersionUID = 1L;
     }
 
-    private static interface ArchiverFactory {
+    private static interface ArchiverFactory extends Serializable {
         Archiver create(OutputStream out);
     }