add wasm cpu

[lizan]

Signed-off-by: Lizan Zhou [email protected]

[katre]

Is wasm a CPU architecture? How is it intended to be used?

[gregestren]

@lizan can you speak more to the concerns expressed in https://github.com/bazelbuild/platforms#adding-a-canonical-constraint-value?

I realize we still need to evolve the process. It's not immediately obvious what belongs in this repo vs. not, and we need clearer agreement on how to even have the right discussions to figure that out.

But the link above is at least a starting point. This is important not just for us (reviewers and PR producer), but anyone else who may ever look at or consider using these.

[lizan]

@katre yes it should be treated as a CPU architecture. Go/Rust and LLVM treat it as an arch.

@gregestren Sure, the wasm32 already defined in rules_rust, 64bit is a future feature so if we don't like, I can remove that. I am working on make this build in proxy-wasm and Envoy WASM integration, this uses cpu value wasm. The bazel C++ Toolchain blog uses asmjs which is quite confusing as well. There should be a canonical constraint settings for this instead of having CPU value defined everywhere.

[lizan]

gently ping?

[katre]

Looking today, sorry again for the delays.

[katre]

Working to merge this now!