compiling dart vm to wasi/wasm as bootstrap

[selfisekai]

this is just an idea, not sure how hard it would get to implement. inspired by zig: https://ziglang.org/news/goodbye-cpp/

• add vm compilation targets for wasi
• allow building sdk using these wasi builds as an alternative bootstrap method (running through wasmtime or other wasi runtime)
• distribute official wasi builds

bootstrapping is a major point of pain from alpine linux perspective - we currently rely on a windows build via wine, which greatly limits available architectures

[mraleph]

Compiling to WASI would:

a) require rewriting parts of the runtime that rely on things like mmap
b) using simulated build (e.g. simarm or simarm64) because Dart VM does not currently have an interpreter.

This is feasible, but hardly optimal. There is a much simpler path towards enabling bootstrap on alpine, outlined in this comment.

I am going to file an issue to track this work, though we are not committing at any concrete timeline yet.

[mraleph]

Filed #51788