This will pull the git repo for haxe, add pleclech as a remote, and build it (on Ubuntu, likely similar commands on Mac. And Windows? Err, sorry.)
Go to your dev folder, checkout HaxeFoundation/haxe repo, and init submodules
git clone https://github.com/HaxeFoundation/haxe.git
cd haxe
git submodule update --init --recursive