[LinuxBIOS] Complete and generic 32bit/64bit support

[Myles Watson]

> 
> Your patch seems ok, except it does not pass -fno-stack-protector through
> to
> mkelfimage anymore, which breaks the build on modern Debian based systems.
> 
> Can you fix that?

Can you help me know how I broke it?  I don't see anywhere that I modified
the flags passed to the compiler in mkelfimage.mk.  I also looked at the
other changes in the patch, but didn't see anything obvious.  I don't have
Debian, so it's less obvious for me.

Thanks,
Myles