I was just trying to give Elixir/Phoenix a shot using the integrated Ubuntu bash on Windows 10. After performing the Elixir installation as described on the homepage I just wanted to install the package manager Hex. Unfortunately this did not work out well.
/usr/local/bin/elixir: 126: exec: erl: Is a directory
After a quick research on Google I quickly stumbled upon this Reddit thread.
So for now to fix this issue you should simply use Erlang version 1:18.3 instead of the latest one. To do this simply install the components as described here.
wget https://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb && sudo dpkg -i erlang-solutions_1.0_all.deb
sudo apt-get update
sudo apt-get install esl-erlang=1:18.3
sudo rm /usr/bin/erl
sudo ln -s /usr/lib/erlang/bin/erl /usr/bin/erl
sudo apt-get install elixir