I've always wondered why there's no Emscripten-like tool, or WASM-like runtime, that shoves your code into a bytecode interpreter embedded within a portable POS

I've always wondered why there's no Emscripten-like tool, or WASM-like runtime, that shoves your code into a bytecode interpreter embedded within a portable POSIX shell-script. With such a thing, nobody would ever have to write actual lowest-common-denominator /bin/sh scripts again. Autotools could just be a Rust program or whatever. (It'd run rather slowly, of course, but you wouldn't use it for the whole process — it'd just be a bootstrapping agent, used to configure the build of a native-compiled build tool.)