Provide binaries for incoming

[abitrolly]

It is impossible to use incoming Emscripten SDK on Travis with Rust. Installing incoming fails with timeout after 40 minutes - https://travis-ci.org/ethereumjs/rustbn.js/jobs/490901840 while installing latest takes only 40 seconds thanks to available binaries.

Docker is unlikely to help, because Rust calls emcc directly.

[kripken]

latest should be very close to incoming - is it not close enough for you?

[abitrolly]

latest fails.

          Unsupported:   %12 = tail call i128 @llvm.bswap.i128(i128 %11) #5
          LLVM ERROR: Instruction not yet supported for integer types larger than 64 bits

https://travis-ci.org/ethereumjs/rustbn.js/jobs/490897289#L632

[kripken]

That looks like a fastcomp bug - try latest-upstream, which we hope to make the default soon anyhow.

[stale]

This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 7 days. Feel free to re-open at any time if this issue is still relevant.

[abitrolly]

@kripken although the build fails https://travis-ci.org/ethereumjs/rustbn.js/jobs/650773025 the installation of latest-upstream is not longer takes 40+ minutes.