Utility for building AtomVM from source

It outputs the artifacts in project_dir/popcorn_runtime_source/artifacts/<target>. To use the built artifacts in Popcorn, configure it with

config :popcorn, runtime: {:path, "popcorn_runtime_source/artifacts/<target>", target: target}

Options:

• git - source repo URL (defaults to FissionVM repo)
• git-ref - branch, tag or commit (only works with the git option)
• path - path to repo source (can be used instead of git)
• target - wasm (default) or unix
• cmake-opts - string with space-separated KEY=VALUE options that will be converted to -DKEY=VALUE cmake options

This is a thin wrapper around scripts/build-atomvm.sh.