This is the multi-threaded compiler: https://github.com/rsaxvc/tcc-swarm

With the multi-threaded tcc above it scales about as well as multiprocess. With mainline it doesn't scale well at all.

So far I haven't gotten around to reusing anything across libtcc handles/instances, but would eventually like to share mmap()'d headers across instances, as well as cache include paths, and take invocation arguments through stdin one compilation unit per line.