@compnerd Thank you so much for writing this up! This is something that I had in mind but wasn't able to approach in a good way due to the amount of other work required to make the WebAssembly port fully functional. It's very hard to strike a balance between "get something working ASAP" and "merge upstream to avoid maintaining forks". The latter is especially hard because it requires a lot of effort to address the review feedback. And the effort is fully justified, but balancing this is very hard wtih limited resources. On the other hand, it's obvious that any improvement to the developer experience will pay off tenfold, so I should focus on that much more.
Do you think that the LLVM/Clang toolchain can also be built separately? I've tried removing llvm-project sources after those are built to get some space cleaned during a CI run, but seems like a lot of stuff from the swift sources directory assumes that headers exist in the llvm-project sibling directory. I'd expect it to look for public headers in the install directory, or at least in the build directory like build/Ninja-ReleaseAssert/llvm-macosx-x86_64. Do you think this behaviour can/should be cleaned up?
With regards to cleaning up the buld system, @kateinoigakukun has spent a substantial amount of work on it as described in the "Separate CMake process into compiler and stdlib" post. It seems like that is blocked by some other pending work with no clear (or at least not public) timeline. How would you recommend to approach it in this situation?