Bustage fix attempt from bug 332115.

modules/zlib/src/mozzconf.h

@@ -37,9 +37,9 @@
 #ifndef MOZZCONF_H
 #define MOZZCONF_H
 
-#ifdef MOZ_ENABLE_LIBXUL
+#if defined(XP_WIN) && defined(ZLIB_DLL)
 #undef ZLIB_DLL
-#elif defined(HAVE_VISIBILITY_ATTRIBUTE)
+#elif defined(HAVE_VISIBILITY_ATTRIBUTE) && !defined(MOZ_ENABLE_LIBXUL)
 #define ZEXTERN __attribute__((visibility ("default"))) extern
 #endif