fix test to not to cause false positives

ext/fileinfo/tests/bug68996.phpt

@@ -1,11 +1,14 @@
 --TEST--
 Bug #68996 (Invalid free of CG(interned_empty_string))
 --SKIPIF--
+<?php
+if (getenv("USE_ZEND_ALLOC") !== "0") {
+    print "skip Need Zend MM disabled";
+}
+?>
 <?php require_once(dirname(__FILE__) . '/skipif.inc'); ?>
 --INI--
 html_errors=1
---ENV--
-USE_ZEND_ALLOC=0
 --FILE--
 <?php
 finfo_open(FILEINFO_MIME_TYPE, "\xfc\x63");