Fix SKIPIF conditions

The test calls `mb_convert_encoding()` and as such requires the
mbstring extension.

ext/dom/tests/bug76738.phpt

@@ -1,7 +1,10 @@
 --TEST--
 Bug #76738 Wrong handling of output buffer
 --SKIPIF--
-<?php require_once('skipif.inc'); ?>
+<?php
+require_once('skipif.inc');
+if (!extension_loaded('mbstring')) die('skip mbstring extension not available');
+?>
 --FILE--
 <?php declare(strict_types=1);
 $test_string = base64_decode('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');