Fix cugraph_c target name in Python builds

[vyasr]

pylibcugraph is currently linking to the cugraph_c target directly rather than via the exported alias cugraph::cugraph_c. I am unsure under exactly what circumstances the former should be working, but I don't think it is reliable. I see failures locally without the change. I have currently made this PR into 22.12 because it seems like an important fix, but I can push it to 23.02 if needed.

[vyasr]

I'd like @robertmaynard's take on whether this is critical to get into 22.12. I'm surprised that this isn't breaking more builds right now since I can reproduce failures without it locally (it won't affect wheel builds, or any other build where the C++ library is built as part of the Python package, but I would expect it to break conda builds). I am curious if the issue in #3041 was just blocking builds from getting far enough to notice this issue.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (branch-22.12@0502585). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

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[robertmaynard]

I'd like @robertmaynard's take on whether this is critical to get into 22.12.

I would say this is critical only if it is blocking getting conda builds out the door. For people building from source we can provide a minimal set of instructions to unblock when building 22.12 locally.

I expect you are correct that #3041 was hiding this issue