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

[Vlad Serebrennikov via llvm-commits]

Endilll wrote:

CI seems to be recovering: https://discourse.llvm.org/t/reduced-pre-commit-ci-bandwidth/80190/7
I'm holding this off further.

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