Use namespaced absl::abseil_dll imported target instead of abseil_dll to correctly propagate CMake usage requirements defined in abseil build on Windows

[traversaro]

Backport of protocolbuffers/protobuf#12978 to fix build failure on Windows such as conda-forge/libignition-msgs1-feedstock#86 (comment) .

xref: conda-forge/conda-forge-pinning-feedstock#4075

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-webservices]

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.

[traversaro]

@conda-forge-admin, please rerender

[github-actions]

Hi! This is the friendly automated conda-forge-webservice.

I tried to rerender for you, but it looks like there was nothing to do.

This message was generated by GitHub actions workflow run https://github.com/conda-forge/libprotobuf-feedstock/actions/runs/5168822075.

[h-vetinari]

Could you adapt the CMake test to load that target if(MSVC) (or equivalent), so that we get some test coverage here?

[traversaro]

Could you adapt the CMake test to load that target if(MSVC) (or equivalent), so that we get some test coverage here?

Sure! I did not fully understand why it is necessary to link a different target on Windows w.r.t. to Unix system, but it should be trivial to add a test.

[traversaro]

Now that I think of, the if logic is handled internally by protobuf, so probably we just need to link protobuf::libprotopuf and everything will work.

[traversaro]

The test is passing fine:

2023-06-04T14:09:03.9269965Z [1/2] Building CXX object CMakeFiles\struct_example.dir\struct_example.cc.obj
2023-06-04T14:09:03.9271237Z [2/2] Linking CXX executable struct_example.exe

[h-vetinari]

Thanks for your work on this (also upstream)!

[github-actions]

Hi! This is the friendly conda-forge automerge bot!

I considered the following status checks when analyzing this PR:

• linter: passed
• azure: passed

Thus the PR was passing and merged! Have a great day!