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

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

We generally avoid XFAIL tests, instead we do normal tests where we expect the wrong behavior and leave a TODO.
In this case UNSUPPORTED makes more sense.

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