9.0 source installations: LoadError from the grpc gem

Upstream issue: https://github.com/grpc/grpc/issues/9998

I am creating this issue for tracking purposes.

The grpc gem contains pre-compiled binary library files for a number of platforms. The pre-compiled libraries work OK. However, when you are on a platform that grpc has no precompiled library files for, it falls back to local compilation during bundle install, and this results in a broken gem installation which throws a LoadError.