Currently x86s select BOOTBLOCK_CUSTOM by default. With this change BOOTBLOCK_CUSTOM is selected only if C bootblock isn't. Change-Id: I218f3b4044175b89697790c82c384b0f85a27ade Signed-off-by: Andrey Petrov <andrey.petrov@intel.com> Reviewed-on: https://review.coreboot.org/13642 Reviewed-by: Aaron Durbin <adurbin@chromium.org> Tested-by: build bot (Jenkins)