gcc-plugins: Rename last_stmt() for GCC 14+

commit 2e3f65cc upstream.

In GCC 14, last_stmt() was renamed to last_nondebug_stmt(). Add a helper
macro to handle the renaming.

Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>