Update emscripten to 1.38.46-upstream

[CryZe]

Rust updated its emscripten version again to a version that uses the upstream LLVM wasm backend that the other Rust wasm targets are also using. cross' docker has been updated accordingly: https://github.com/rust-lang/rust/pull/63649/files#diff-3334ef4d3e22f40ded09f2045806021f

[reitermarkus]

Have you looked into the CI failure?

[CryZe]

I don't think I have as I had very little time. But it seems like it can't find the build when trying to access it now.

[reitermarkus]

Weird, I also can't access it anymore now.

[reitermarkus]

bors try

[bors]

try

Build failed

• rust-embedded.cross

[CryZe]

The failures seem to be:

For asmjs: note: shared:ERROR: wasm2js does not support source maps yet (debug in wasm for now)
For wasm32: note: shared:ERROR: BINARYEN_TRAP_MODE is not supported by the LLVM wasm backend

We'll have to dig deeper what they mean.

[CryZe]

Actually I believe the problem could be it using the new emcc but an old Rust compiler (the change is only on nightly).

The docker images don't contain the Rust compiler right? So essentially only the tests would need to be updated to use the nightly compiler instead.

[reitermarkus]

The docker images don't contain the Rust compiler right?

Yes, the compiler is mounted via a volume.

So essentially only the tests would need to be updated to use the nightly compiler instead.

Would this not break using stable Rust then?

[CryZe]

Yeah we should probably release this with 1.40

[reitermarkus]

Emscripten has been updated in #361 but the C++ test is failing and has been disabled for now. libstdc++ cannot be found, no idea what the problem is.

[CryZe]

I'm also not planning on using emscripten anymore, so if this PR is still necessary for anyone, feel free to create a new one.