Run scandir overflow test on Windows only (#22934)

Avoids creating 70,000 files on platforms unaffected by the Win32 DIR_W32.offset regression. Shaves ~9s off non-Windows test runs.

Author: NickSdot

ext/standard/tests/file/bug36365.phpt

@@ -2,6 +2,7 @@
 Bug #36365 (scandir duplicates file name at every 65535th file)
 --SKIPIF--
 <?php
+if (PHP_OS_FAMILY !== 'Windows') die('skip Windows only');
 if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
 ?>
 --FILE--