Rustflags now require alsow +mutable-globals

[Ciantic]

I spent quiet some time wondering about linker errors, looks like RUSTFLAGS with latest nightly needs also mutable-globals, e.g.

-C target-feature=+atomics,+bulk-memory,+mutable-globals

See e.g. rustwasm/wasm-bindgen#2487 and the appropriate fix alexcrichton/wasm-bindgen@ad53c12

[RReverser]

looks like RUSTFLAGS with latest nightly needs also mutable-globals,

Yeah those things tend to change / break over time which is why the README specifically recommends a fixed nightly version. I suppose we can upgrade that version at some point + update the required flags though.

[RReverser]

Actually, if you can find a nightly hash that corresponds to latest stable Rust (we do this to reduce risks), I'd be happy to accept a PR that updates the Rust version & required features.