[skip ci] Mark stack limit tests with high memory limit as slow

Author: iluuu1994

Zend/tests/stack_limit/stack_limit_001.phpt

@@ -3,6 +3,7 @@ Stack limit 001 - Stack limit checks with max_allowed_stack_size detection
 --SKIPIF--
 <?php
 if (!function_exists('zend_test_zend_call_stack_get')) die("skip zend_test_zend_call_stack_get() is not available");
+if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
 ?>
 --EXTENSIONS--
 zend_test

Zend/tests/stack_limit/stack_limit_006.phpt

@@ -3,6 +3,7 @@ Stack limit 006 - env size affects __libc_stack_end
 --SKIPIF--
 <?php
 if (!function_exists('zend_test_zend_call_stack_get')) die("skip zend_test_zend_call_stack_get() is not available");
+if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
 ?>
 --EXTENSIONS--
 zend_test

Zend/tests/stack_limit/stack_limit_014.phpt

@@ -3,6 +3,7 @@ Stack limit 014 - Fuzzer
 --SKIPIF--
 <?php
 if (!function_exists('zend_test_zend_call_stack_get')) die("skip zend_test_zend_call_stack_get() is not available");
+if (getenv("SKIP_SLOW_TESTS")) die('skip slow test');
 ?>
 --EXTENSIONS--
 zend_test