Tracking Issue for Multi Value WASM

[CryZe]

Multi-value (+multivalue) is available in all browsers, but Rust seems to have trouble dealing with the ABI change. std is precompiled without multi value, so std is incompatible with your own crates that are compiled with the feature. We may need to build std ourselves with the nightly compiler.

[CryZe]

There's two problems with -Z build-std. First of all, it seems to not be able to build std if we activate multivalue, but even if it did, -Z build-std finds the preinstalled std and then complains that it found two versions of std. So yeah this isn't ready at all, I probably need to ping Alex Crichton what the status of / plan for multivalue is.