Surprisingly, it took until last year for someone to actually ask Ken for the code: https://research.swtch.com/nih
It's such a well-written article.
Here's previous HN discussion about it:
Running the "Reflections on Trusting Trust" Compiler - https://news.ycombinator.com/item?id=38020792 - Oct 2023 (67 comments)
(posted by rsc himself!)