amaranth-yosys doesn't build on MacOS

[Rob Taylor]

Numerous issues are hit when building on MacOS (tested on Montaray and Ventura):

1. Assumes GNU tools behaviour
2. downloads linux WASI SDK
3. forces wasmtime < 0.33 - M1/M2 require at least 0.40.1

[Catherine]

It's not supposed to build on macOS. However, the wasmtime dependency should be relaxed; I'll do this in a moment.

[Catherine]

Relaxed the version requirement in af2958d.

[Catherine]

@robtaylor has confirmed that https://pypi.org/project/amaranth-yosys/0.10.0.dev47/ works on macOS.