[clang] [clang-tools-extra] [clang] Complete fields in __builtin_offsetof designators (PR #195126)

[Yanzuo Liu via cfe-commits]

https://github.com/zwuis commented:

Could you please add tests with bit-fields, which should not be the second argument of `offsetof`?

https://github.com/llvm/llvm-project/pull/195126