The Kconfig stage (arch/Kconfig) has already evaluated whether the
compiler supports -fno-stack-protector.

You can use CONFIG_CC_HAS_STACKPROTECTOR_NONE instead of invoking
the compiler to check the flag here.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>