[clang] [clang-repl] Emit const variables only once (PR #65257)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> That looks good to me. Can we backport that to the llvm17 release branch? I know at least one downstream project that jumps through hoops to support this.

I'd say we should not backport to 17.0.0; we need to get the final rc out the door and this isn't fixing a critical bug or regression. However, it may be reasonable to consider for 17.0.1+

https://github.com/llvm/llvm-project/pull/65257