[codezero]

This isn't the same, but if you're interested in looking at a compiler and OS mostly from scratch based on C check this out. It's pretty amazing. https://github.com/rswier/swieros

It comes from the author of the c4 compiler. (Interpreter?)

[sklogic]

Shameless plug: there is also mine kinda-C-based setup (but I also have a somewhat unfinished Oberon compiler too): https://github.com/combinatorylogic/soc