[mlir] [clang] [clang-tools-extra] [llvm] Make clang report garbage target versions. (PR #75373)

[Fangrui Song via llvm-commits]

MaskRay wrote:

In addition, calling `exit` from library code is probably not good. The error can be surfaced by a very top-level component (e.g. driver as @zmodem mentioned).

https://github.com/llvm/llvm-project/pull/75373