Why use a custom compiler for one specific target when you could have a single compiler that support any target you want? It doesn’t look like emscripten has an integrated build system either?

I think that’s the genius of Zig.. one of the main goals is to build a better and faster C compiler. It might end up being the only C compiler with really solid hot-swapping support. And then if you’re already using the compiler you might as well start using the language too.