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

[Aaron Puchert via cfe-commits]

aaronpuchert wrote:

Same for `if (MSVC)`. So let's make this:
```cmake
if (NOT CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND
    NOT MSVC AND NOT LLVM_LINKER_IS_SOLARISLD AND NOT MINGW)
```

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