openat/openat02.c: add a new case to test flags

create a new case to test flags for openat(2):
O_APPEND
O_CLOEXEC
O_LARGEFILE
O_NOATIME
O_NOFOLLOW
O_TRUNC

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/configure.ac b/configure.ac
index a0eca26..8698c47 100644
--- a/configure.ac
+++ b/configure.ac
@@ -177,6 +177,7 @@
 LTP_CHECK_FCHOWNAT
 LTP_CHECK_MKNODAT
 LTP_CHECK_READLINKAT
+LTP_CHECK_OPENAT
 LTP_CHECK_FALLOCATE
 LTP_CHECK_SYSCALL_FCNTL
 LTP_CHECK_SYSCALL_PERF_EVENT_OPEN