Many of you might be aware that the code has been modified into pure GCC-only code in the Low Cost Embedded x86 Teaching Tool article. I need to migrate that code as well. But, I'm quite sure it will require special GCC version to be able to emit the correct binary, akin to the one used by Coreboot. I'll post an update once I've updated that one as well.
Anyway, it's rather surprising to me that using Nasm + GCC is more future-proof compared to using GCC alone. It shows that you can't be really sure about the future-proof-ness of the toolset you used for software development.