The Whitesmiths #C compiler:
https://github.com/hansake/Whitesmiths-C-compiler
by PJ Plauger, et al.
I remember this & the #Idris OS from recent episodes of the #AdventOfComputer podcast.
Via HN: https://news.ycombinator.com/item?id=44356130
On Lobsters: https://lobste.rs/s/ybarpv/whitesmiths_c_compiler_one_earliest