[1.46] shared abseil on windows + test overhaul

[h-vetinari]

Picking up various improvements from #237, but switching to shared abseil builds on windows now.

[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.

[h-vetinari]

Yay, passing windows builds, including a full-fledged configure+build test for using the produced artefacts through cmake. 🥳

Unix still needs conda-forge/libprotobuf-feedstock#127 / conda-forge/libprotobuf-feedstock#128 (if we want to also switch on the cmake example).

@conda-forge/grpc-cpp @hmaarrfk PTAL

PS. The commits are most likely easier to review individually.
PPS. For reasons that are completely inscrutable to me, the tests for grpc-cpp on windows do not run the file checks under commands:, or at least do not show their output. Not sure if the compiler activation is interfering with that. If we really want, we could also do a specific testing feedstock that gets triggered through downstreams: like libcxx does with libcxx-testing.

[hmaarrfk]

I don't think I'll be of much use to review and as such, i would like to take a back seat on this.

I think you have many capable users of the library that might be able to give you feedback better than i can.

I think i remember reading that "abseil shared will compile, but for some reason using it is problematic" which i don't really understand. As such, i would encourage you to build up as much of the stack as you can and try to test it for real.

It is possible to use conda forge infrastructure to upload to your own channel. It is great for experimenting purposes considering build locally doesn't work for windows. The manual steps i have to do is activate azure and enter in my binstar token there.

[h-vetinari]

I don't think I'll be of much use to review and as such, i would like to take a back seat on this.

Fair enough.

I think i remember reading that "abseil shared will compile, but for some reason using it is problematic" which i don't really understand.

The issue is precisely the ABI-impact of the C++ version (and being susceptible to breakage because even the headers that come along with the shared lib can change based on the C++ standard used to compile consuming projects). Most people aren't ready to take on the consequences of doing that, but our abseil unix builds have been shared for quite a while.

As such, i would encourage you to build up as much of the stack as you can and try to test it for real.

It is possible to use conda forge infrastructure to upload to your own channel. It is great for experimenting purposes considering build locally doesn't work for windows. The manual steps i have to do is activate azure and enter in my binstar token there.

I can imagine this using a dev-channel that we can publish to (similar to llvm_rc or simply reusing the existing abseil_dev label) etc., but I don't think that's even necessary. The testing added in this PR should really put all worries to rest (including pkg-config!).

[hmaarrfk]

This looks really clean and high quality.