[clang] [clang-tools-extra] [lldb] [llvm] [mlir] Remove unused variables in the monorepo (PR #204994)

[Nikolas Klauser via cfe-commits]

philnik777 wrote:

While I'm generally not a fan of multi-project patches I think this should be small enough to land in one go. If people think this should be split per sub-project I can do that as well though.

https://github.com/llvm/llvm-project/pull/204994