Add test for GH-15909 (fixed by previous IR update)

ext/opcache/tests/jit/gh15909.phpt

@@ -0,0 +1,16 @@
+--TEST--
+GH-15909 (Core dumped in Core dumped in ext/opcache/jit/ir/ir_cfg.c)
+--EXTENSIONS--
+opcache
+--INI--
+opcache.jit=1001
+opcache.jit_buffer_size=64M
+--FILE--
+<?php
+function foo() {
+for(;x;)for(;$fusion=1;);
+}
+?>
+DONE
+--EXPECT--
+DONE