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

[Arthur Eubanks via cfe-commits]

aeubanks wrote:

This was with `-DLLVM_ENABLE_LLD=ON`, so probably not? I'm guessing there's some CMake logic that doesn't fit with clang-repl's expectation of symbol availability, but that may be wrong.

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