Failed to parse metadata - Newline escaping

I'm trying to compile a block of code within an `EM_JS` macro. The offending piece is here, which does not link and fails to parse metadata.

`headers.trim().split(/[\r\n]+/);`

The problem is the `\` escape sequences, so, of course the next step is to escape the escapes.

`headers.trim().split(/[\\r\\n]+/);`

Linking succeeds, but the final javascript will contain an emitted actual newline character, like so.

```
headers.trim().split(/[\r\
]+/);
```

Which results in an exception being thrown for an invalid regex expression. Is there any workaround here? I did a little digging, and my best guess is that [this code](https://github.com/WebAssembly/binaryen/blob/master/src/wasm/wasm-emscripten.cpp#L193-L220) is finding the escaped newline and adding in one more escaped `\` character, which simply creates a real newline character in the output. Though I'm not sure about this.