[opam] Package build fails on builder

[rsertelon]

As @elliott-davis told me earlier today, it is related to the make ext-lib target of the package, and tar trying to keep uid/gid to 1000 which seems to be disallowed on builder.

See https://bldr.habitat.sh/#/pkgs/core/opam/builds/948615593770295296 for more information

[baumanj]

This one might be a little bit tricky to fix. I think the line you'll need to change is this one, and possibly this one too.

If you can add in --no-same-owner, it will prevent tar from trying to chmod the extracted files according to the ownership recorded in the archive. That's tar's default behavior when running with euid 0 as it does in airlock on builder.

[rsertelon]

Thank you for the input :) I have tried another solution that means packaging the deps that are downloaded as habitat packages. I don't know which is best actually. @elliott-davis seemed to think packaging the deps was best IIRC (on slack).

[smacfarlane]

Wit the change to Builder to use docker-based builds, and #2453 opam is able to build on Builder.