Step 6: Allow Abseil to be installed and used with find_package() #111
Description
This has been a contentious one, but yes, Abseil is going to support the git clone; make; make install workflow.
This will come at the same time as Abseil cuts our first Long Term Support Branch -- basically cuts of our source code stuck in versioned inline namespaces which we will maintain for a length of time with emergency security bugfixes and the like, and which will also be tagged for use by package managers and the like. Ideally, the find_package() workflow will only work with Long Term Support branches of Abseil -- it's the only safe way to use a precompiled version of abseil, as we can make sure that symbols don't clash unless they're identical (as long as they're compiled and linked with the same settings, etc). So the supported usages of abseil will be either live-at-head using Bazel, a mirror, a git submodule, or config-time downloading of source as in googletest's model, or using a precompiled Long Term Support branch of Abseil. It's unclear as of yet how this can be accomplished -- discussion on this point will happen closer to the point in time we're ready for this step.