[clang] [llvm] Add __attribute__((visibility("default"))) attribute to certain symbols to stop them being hidden when linking clangInterpreter library to other libraries during Emscripten build (PR #146786)

[Saleem Abdulrasool via llvm-commits]

compnerd wrote:

I think that it might be better to wait on this change until we do this properly. In the mean time, the workaround would be to use `-fvisibility=default`. If you want to help with the annotations to make clang build as a DSO, I think that @andrurogerz would welcome the help. But, this change should be split up so that it can be easily reviewed similar to how we have been approaching the LLVM side.

https://github.com/llvm/llvm-project/pull/146786