better use getter than raw attribute access

src/main/org/apache/tools/zip/ZipEntry.java

@@ -136,9 +136,10 @@ public class ZipEntry extends java.util.zip.ZipEntry implements Cloneable {
         setInternalAttributes(entry.getInternalAttributes());
         setExternalAttributes(entry.getExternalAttributes());
         setExtraFields(entry.getExtraFields(true));
-        setPlatform(entry.platform);
-        setGeneralPurposeBit(entry.gpb == null ? null :
-                             (GeneralPurposeBit) entry.gpb.clone());
+        setPlatform(entry.getPlatform());
+        GeneralPurposeBit other = entry.getGeneralPurposeBit();
+        setGeneralPurposeBit(other == null ? null :
+                             (GeneralPurposeBit) other.clone());
     }
 
     /**