Skip test case on non Windows platforms

Author: cmb69

ext/ffi/tests/bug78270_2.phpt

@@ -3,6 +3,8 @@ FR #78270 (Usage of __vectorcall convention with FFI)
 --SKIPIF--
 <?php
 require_once('skipif.inc');
+if (substr(PHP_OS, 0, 3) != 'WIN') die("skip this test is for Windows platforms only");
+
 $dll = 'php7' . (PHP_ZTS ? 'ts' : '') . (PHP_DEBUG ? '_debug' : '') . '.dll';
 try {
     FFI::cdef(<<<EOC