Both google-cloud-cpp and gRPC depend on Abseil. We need to refactor the Abseil build to its own macro so it can be more easily reused.

Reporter: Carlos O'Ryan / @coryan
Assignee: Carlos O'Ryan / @coryan

Related issues:

• [C++] Add filesystem / IO implementation for Google Cloud Storage (blocks)

PRs and other links:

• GitHub Pull Request #11261

_{Note: This issue was originally created as ARROW-14157. Please see the migration documentation for further details.}