Install Emscripten SDK

ekx cli requires Emscripten SDK to build Web Target. By default ekx cli try search Emscripten SDK in path ~/dev/emsdk, but you could override that with system environment variable EMSDK. In case if you don't have Emscripten SDK installed there is instruction:

# Go to your HOME `dev` folder
cd ~/dev

# Get the emsdk repo
git clone https://github.com/emscripten-core/emsdk.git

# Enter that directory
cd emsdk

# Fetch the latest version of the emsdk (not needed the first time you clone)
git pull

# Download and install the latest SDK tools.
./emsdk install latest

# Make the "latest" SDK "active" for the current user. (writes .emscripten file)
./emsdk activate latest