CONFIG_FORTIFY_SOURCE detects various overflows at compile-time.
(6974f0c4 ("include/linux/string.h:
add the option of fortified string.h functions)

ARCH_HAS_FORTIFY_SOURCE means that the architecture can be built and
run with CONFIG_FORTIFY_SOURCE.

Since ARM can be built and run with that flag like other architectures,
select ARCH_HAS_FORTIFY_SOURCE as default.
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>