Add a header that will make the checker script think that it is dealing
with a x86_64 config file. Additionally, update the stackprotector
related options to reflect the >= 4.18 names.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

Thanks to @Bernhard40 for a nice idea.

The file indicates where you can find kernel configurations.

config check is NOT PASSED: 56 errors

Source: https://kernel.opensuse.org/cgit/kernel-source/plain/config/x86_64/default?h=SLE15

config check is NOT PASSED: 58 errors