Not all compilers, notably GCC < 10, have support for
__attribute__((no_stack_protector)).
Fall back to a mechanism that also works there.

Tested with GCC 9.5.0 from kernel.org crosstools.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>