[clang] [clang-repl] Lay the foundation of pretty printing for C. (PR #89811)

[Arthur Eubanks via cfe-commits]

aeubanks wrote:

So actually even the `export_executable_symbols_for_plugins` doesn't fix our bots. I've narrowed it down to `-DLLVM_ENABLE_PIC=ON/OFF`. Perhaps we're not exporting symbols when `-DLLVM_ENABLE_PIC=OFF`.

https://github.com/llvm/llvm-project/pull/89811