[3.20] Build with CMake on unix

[h-vetinari]

Testing things like grpc through the examples provided upstream needs find_package(protobuf) to run, which fails on unix with

CMake Error at /home/conda/feedstock_root/build_artifacts/grpc-split_1662220567868/test_tmp/examples/cpp/cmake/common.cmake:101 (find_package):
  Could not find a package configuration file provided by "Protobuf" with any
  of the following names:

    ProtobufConfig.cmake
    protobuf-config.cmake

  Add the installation prefix of "Protobuf" to CMAKE_PREFIX_PATH or set
  "Protobuf_DIR" to a directory containing one of the above files.  If
  "Protobuf" provides a separate development package or SDK, be sure it has
  been installed.

because the builds here are done with autotools.

Build with cmake to be able to run better testing in grpc-cpp feedstock. Also:

• normalize cmake module location on windows
• unify build scripts
• improve testing

[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]

@conda-forge/libprotobuf PTAL

We've had a bunch of issues with abseil/grpc and recent migrations, some of which only show up when actually trying to build against the artefacts in other feedstocks (e.g. things around the link interface and what libs are necessary at runtime because of that), so I'd like to run the compilation example from upstream grpc in our CI, see the setup added in conda-forge/grpc-cpp-feedstock#239.

However, that example is based on cmake and currently fails because our libprotobuf builds have no cmake metadata. Since upstream protobuf seems to have put much more effort behind CMake (as of 3.21, cmake/CMakeLists.txt is deprecated, as there's now a CMakeLists.txt in root), I think this is a good thing to do. It harmonizes the build scripts and should make them easier to understand.

As I went, I fixed some other issues like improved testing, normalized the location of the cmake metadata on windows, and harmonized the static build setup for windows with the unix ones resp. conda-forge/conda-forge.github.io#1809. I also switched away from travis as it consistently killed the build (not sure if memory demands are too high...?).

This PR has a mirror version in #128 for main, but it should be enough to review this one. I've kept as much as possible intact through the various commits, which should be easier to review than the whole diff at once (which loses the files renames).

[xylar]

I'm new to this feedstock but this looks like a really great improvement @h-vetinari!

[h-vetinari]

@conda-forge/protobuf
I will merge this & #128 tomorrow, Tuesday unless there are objections until then.

Thanks for the review @xylar!