[clang] [clang][python][test] Move python binding tests to lit framework (PR #142948)

[Rainer Orth via cfe-commits]

rorth wrote:

> Thank you for the PR, imo this is a much better approach than the previous one.

Thanks.  The previous approach was just a minimal fix (hack?) to avoid breaking the build in a specific situation.  This one (if completed) should handle all known issues with Python bindings testing.

> As I mentioned before, I'm not familiar with the testing infrastructure, but insofar as it works, this looks good to me.

It will certainly need more testing in situations currently covered by `RUN_PYTHON_TESTS` that I known nothing about and probably cannot test myself.

> Do note that the libclang CI should also be adapted: `.github/workflows/libclang-python-tests.yml` The target it uses doesn't exist anymore, and the paths that trigger the workflow should also be changed to remove the old path and include `clang/tests/bindings/python`. You can now also remove the trigger on `clang/CMakeLists.txt`, which should make this run far less often on unrelated PRs.

Ah, I see.  I've made the obvious adjustments locally, but am at a bit of a loss how to handle `build_target` now.  Doing this manually would be an invocation of `bin/llvm-lit clang/test --filter=bindings/python` or some such.  Maybe a new implementation of the `check-clang-python` target needs to be introduced? Don't know if/how I can test this myself.

https://github.com/llvm/llvm-project/pull/142948