Fix skipif to resolve the common reason this test fails

ext/phar/tests/bug52013.phpt

@@ -6,7 +6,10 @@ http://bugs.php.net/bug.php?id=52013
 --CREDITS--
 Frederic Hardy frederic.hardy@mageekbox.net
 --SKIPIF--
-<?php if (!extension_loaded("phar")) die("skip"); ?>
+<?php
+if (!extension_loaded("phar")) die("skip");
+if (!extension_loaded("zlib")) die("skip test needs zlib extension enabled to compress archives with gzip");
+?>
 --INI--
 phar.require_hash=0
 phar.readonly=0