[clang] [clang] fix range of empty enumeration without fixed underlying type (PR #106841)

[via cfe-commits]

keinflue wrote:

@frederick-vs-ja This is currently considered in [CWG 2932](https://cplusplus.github.io/CWG/issues/2932.html). I will close this until there is a decision.

https://github.com/llvm/llvm-project/pull/106841