os_based_configure_options cannot bail early about asdf-ruby

[akerl]

On a related note, I'm curious about the utility of ASDF_PKG_MISSING. It's set inside os_based_configure_options, but doesn't bubble up since it's using a subshell, so it'll always be empty everywhere it's used.

[Stratus3D]

For the asdf-erlang plugin we are moving away from strictly requiring homebrew to be installed to just asserting that the dependencies are present. That's another thing that should probably be changed here too.

[iloveitaly]

This code does not exist in this plugin anymore, I think this issue is safe to close out.

For anyone else who lands on this page via google, code setting ASDF_PKG_MISSING in various asdf packages looks like it was copy/pasted from a plugin way back. The variable is not used by the core asdf package and does nothing when set unless there's conditional logic to check for it within the asdf plugin script.