Tighten co-installability of new builds

[h-vetinari]

Fix oversight from #35

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[hmaarrfk]

isn't the whole point to allow

• Package a depend on abseil V2 (shared)
• Package b depends on abseil V1 (static) AND a

How can one build package b now?

[h-vetinari]

isn't the whole point to allow [...]

Not for abseil, because the ABIs differ (shared is C++17, static may be C++11 / C++14). If one of your deps depends on shared abseil, you have to use shared abseil as well, or move to C++17 (in which case you can also use the static lib again, see this PR).

But feel free to join into a serendipitously timed discussion that concerns this: #43