I ended up installing it on my work laptop - hours of downloading later - pulled down my repo, and the same problem! An odd emscripten error that seemingly only two people on the internet had ever had before. Fun times until 2am, but hey that's developer life!!
Fortunately I'd taken today off work and was able to resolve it this morning by creating a fresh project and porting across the changes.
Hope you enjoyed the gamejam and you got it working in the end.