LLVM is recommended as a replacement of Fastcomp. See
Thanks for opening this topic franklinyu!
In Emscripten we are hoping to switch the default backend to LLVM soon (more details and background), but it looks like currently Homebrew only supports the old fastcomp backend. So it would be good to support the new one - it’s better, and it’s the one we’ll be supporting for the long term.
We have docs about packaging Emscripten with the new backend which hopefully can help here. I’m afraid I don’t know much myself about Homebrew, but I can help with any questions on the Emscripten side!