message: Update emsdk version in README.
diff: @@ -375,7 +375,7 @@ same version that our continuous builds use.
  ```
  cd <your chosen parent folder for the emscripten SDK>
  -curl -L https://github.com/emscripten-core/emsdk/archive/1.39.19.zip > emsdk.zip
  +curl -L https://github.com/emscripten-core/emsdk/archive/2.0.12.zip > emsdk.zip
  unzip emsdk.zip ; mv emsdk-* emsdk ; cd emsdk
  python ./emsdk.py install latest
  python ./emsdk.py activate latest
  