Update ext/mbstring/tests/gh21036.phpt

Author: youkidearitai

ext/mbstring/tests/gh21036.phpt

@@ -2,6 +2,10 @@
 GH-21036 (mb_ereg_search_getregs() after regex cache invalidation)
 --EXTENSIONS--
 mbstring
+--SKIPIF--
+<?php
+if (!function_exists("mb_ereg")) print "skip mb_ereg() not available";
+?>
 --FILE--
 <?php
 error_reporting(E_ALL & ~E_DEPRECATED);