[PSA] emscripten 4.0 is coming soon

[Sam Clegg]

Occasionally we (semi-arbitrarily) decide to bump the major version of emscripten.

In this case it does coincide with a few significant updates:

-  The default Safari version targeted by Emscripten has been raised from 14.1      

  to 15.0 enabling 3 features to be turned on by default:

  1. wasm bulk-memory proposal

  2. wasm non-trapping float-to-int proposal

  3. WASM_BIGINT JavaScript bigint integration with i64
- LLVM libraries (ompiler-rt, libcxx, libcxxabi) updated for v19
- Internal usage of async/await by default

For a more completely list of changes see the changelog: https://github.com/emscripten-core/emscripten/blob/main/ChangeLog.md

Hopefully we will release this in the next few days.

cheers,

sam