[clang] [clang][python][test] Check if libclang.so is loadable (PR #142353)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

@rorth Now that https://github.com/llvm/llvm-project/pull/142371 is merged, can you re-evaluate this PR and update the description?

https://github.com/llvm/llvm-project/pull/142353