[clang] [llvm] Introduce symbol versioning for clang-cpp (PR #116556)

[Aaron Puchert via cfe-commits]

aaronpuchert wrote:

We don't run into the same issue with the `LLVM` library because `LLVM_BUILD_LLVM_DYLIB` defaults to off. There is no counterpart toggle for `clang-cpp`, so it's being built on the bot. I suppose that with `-DLLVM_BUILD_LLVM_DYLIB=ON` the bot would also run into issues with `LLVM`.

https://github.com/llvm/llvm-project/pull/116556