Gitpod (don't do this, use asdf)

.gitpod.apt.Dockerfile

FROM gitpod/workspace-full

USER gitpod

# Erlang: https://computingforgeeks.com/how-to-install-latest-erlang-on-ubuntu-linux/
RUN wget -O- https://packages.erlang-solutions.com/ubuntu/erlang_solutions.asc | sudo apt-key add -
RUN echo "deb https://packages.erlang-solutions.com/ubuntu focal contrib" | sudo tee /etc/apt/sources.list.d/rabbitmq.list

RUN sudo apt-get update && \
    sudo apt-get install inotify-tools -y && \
    sudo DEBIAN_FRONTEND=noninteractive apt-get install erlang=1:22.2.7+dfsg-1 -y && \
    sudo apt-get install elixir=1.9.1.dfsg-1.3 -y && \
    sudo apt-get clean && \
    sudo rm -rf /var/cache/apt/* && \
    sudo rm -rf /var/lib/apt/lists/* && \
    sudo rm -rf /tmp/*

RUN mix local.hex --force \
    && mix local.rebar --force

.gitpod.asdf.Dockerfile

FROM gitpod/workspace-full

USER gitpod

RUN brew install asdf
RUN asdf plugin add erlang && \
    asdf plugin add elixir && \
    asdf plugin add postgres
  
# install everything in .tool-versions
RUN asdf install
RUN echo 'export PATH=$PATH:/$HOME/.asdf/shims' >> .bashrc
# Success. You can now start the database server using:
# /home/gitpod/.asdf/installs/postgres/11.4/bin/pg_ctl -D /home/gitpod/.asdf/installs/postgres/11.4/data -l logfile start

RUN mix local.hex --force && \
    mix local.rebar --force

.gitpod.brew.Dockerfile

FROM gitpod/workspace-full

USER gitpod

# Erlang/OTP 23.3.3
RUN brew install erlang -v

# Elixir  1.11.4
RUN brew install elixir

RUN mix local.hex --force && \
    mix local.rebar --force