tools/nolibc: tests: fold in no-stack-protector cflags

For the cflags to enable stack protectors to work properly they need to
be specified after -fno-stack-protector.

To do this fold all cflags into a single variable and move
-fno-stack-protector before the arch-specific cflags and another
one specific to stack protectors since we don't want to enable them
on all archs.

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>