Better support for C++ Sandwich

If I understand correctly, `rules_go` supports C++ Sandwich s.t. `go_library` can have `.{c,cc,h,..}` sources and depend on `cc_library`. It would be great if that was also possible the other way around, but that currently fails because `go_library` doesn't return `CcInfo`.

I did some experiments regarding such an implementation and somehow succeeded to expose the C++ headers to other `cc_library` targets. However, linking the final binary failed because I could figure out how to get the correct archives (i.e. `.a`) for the Go targets.

Any help regarding this issue would be greatly appreciated.

Start by reproducing the reported failure with a go_library consumed by a cc_library and linked into a final binary. Read the rules_go handling of CcInfo and the archive outputs involved; done means C++ targets can consume Go targets and the final binary links successfully.

Written by the indexing model from the issue text.