Skip two curl tests under asan

These tests leak with the curl version on ubuntu 20.04. This should
be fixed when we switch exit to use an exception.

Author: nikic

ext/curl/tests/bug68937.phpt

@@ -3,6 +3,7 @@ Bug # #68937 (Segfault in curl_multi_exec)
 --SKIPIF--
 <?php
 include 'skipif.inc';
+if (getenv('SKIP_ASAN')) die('skip some curl versions leak on longjmp');
 ?>
 --FILE--
 <?php

ext/curl/tests/bug68937_2.phpt

@@ -3,6 +3,7 @@ Bug # #68937 (Segfault in curl_multi_exec)
 --SKIPIF--
 <?php
 include 'skipif.inc';
+if (getenv('SKIP_ASAN')) die('skip some curl versions leak on longjmp');
 ?>
 --FILE--
 <?php