parallel debuginfo for kernel (plus hardening flags)

[Laura Abbott]

Hi,

The kbuild kernel maintainer has accepted the last changes needed for
unique build ids upstream so I went ahead and applied the series to
rawhide. This means that parallel debuginfo should actually
work for future kernel builds. As part of this change, I also enabled
the hardening flags for the few userspace binaries that get shipped
with kernel-devel. I don't expect either of these changes to break
anything but as always if you find any issues, please file a bug.

Thanks,
Laura