[llvm] [clang] Disable runtimes testing in C++03 and Clang modules modes (PR #99303)

[Louis Dionne via llvm-commits]

https://github.com/ldionne approved this pull request.

This sucks, but it's more important to keep CI working effectively than to keep a high coverage. We should talk with the LLVM Foundation about these bandwidth issues. I find it unfortunate that we can't afford to test our code properly given how important and fundamental LLVM to a lot of organizations with significant resources.

https://github.com/llvm/llvm-project/pull/99303