[skip ci] Fix 64-bit only test

Author: iluuu1994

ext/opcache/tests/jit/gh12481.phpt

@@ -3,6 +3,10 @@ GH-12481: PHP crash on Windows 64-bit with JIT enabled
 --INI--
 opcache.enable=1
 opcache.enable_cli=1
+--SKIPIF--
+<?php
+if (PHP_INT_SIZE !== 8) die('skip 64-bit only');
+?>
 --FILE--
 <?php
 function foo(&$var) {