Ghost Directory + Debugging Question

[Sean Gribbin]

Hi folks,

I hope this is the correct way to ask for some help. I've recently cloned
Grub2's code so I can try and add some functionality for a secure boot
chain.
I was looking at a friend's modifications to GRUB and noticed that they
include <grub/cpu/io.h> but there is no cpu directory that exists (and
subsequently, no io header).
Confused, I checked GRUB's repo to see if the cpu directory exists and
low-and-behold, it doesn't:
https://git.savannah.gnu.org/cgit/grub.git/tree/include/grub.

What am I missing here?

In addition, this is my first time setting up a GRUB development
environment. My research has led me to install GDB. Is using GDB + a CLI
the "correct" way to debug and step through GRUB?

Thanks,
Sean