wasm-opt Tool version should be bumped

[michelhe]

🐛 Bug description

The prebuilt wasm-opt version_90 segfaults when optimizing my crate with -enable-mutable-globals.
When I manually use version_97, it works

I think it will also help fix #886

🤔 Expected Behavior

👟 Steps to reproduce

I didn't try to test any other project, but It specifically segfaults in mine: https://github.com/michelhe/rustboyadvance-ng/tree/master/platform/rustboyadvance-wasm
add to Cargo.toml

[package.metadata.wasm-pack.profile.release]
wasm-opt = ["-Oz", "--enable-mutable-globals"]

run wasm-pack build --release

🌍 Your environment

wasm-pack version: 0.9.1
rustc version: rustc 1.43.0 (4fb7144ed 2020-04-20)

[panstromek]

For the record, I had the same issue, reported it in binaryen:

WebAssembly/binaryen#3513