Use proto_common module in lua_proto_library

[comius]

This handles all the paths correctly and reduces the code size. It should work correctly also internally.

Fixes: https://github.com/protocolbuffers/upb/issues/784

[haberman]

Thanks for the change but we cannot do this yet. We need to support the two most recent Bazel LTS versions per our policy:

https://opensource.google/documentation/policies/cplusplus-support#3_build_systems

Until proto_common is supported in the latest two LTS releases, we cannot use it.

Is there a way to make this conditional on the availability of proto_common?

[comius]

I'm reluctant to fix workarounds in upb, that are broken with fixes in proto_library for LTS release: https://github.com/protocolbuffers/upb/issues/784

It doesn't sound like a good use of my time.

@meteorcloudy, can we disable upb in downstream test and reenable it after LTS is released?

[haberman]

I repeat my previous question:

Is there a way to make this PR conditional on the availability of proto_common?

If we could use the new code-paths when a newer Bazel is available, we would not need to disable upb.

[haberman]

For example, if we could test the Bazel version from Starlark, we could achieve both goals (support old Bazel versions and have less buggy behavior with newer Bazels).

[comius]

Please hold this PR until after LTS.

[haberman]

I don't think one LTS will be enough. We need to support the two most recent LTS releases. So we will need to wait until proto_common is in the last two LTS releases.