[clang] [clang-format] Fix short function merging with macro expansion (PR #204421)

[via cfe-commits]

owenca wrote:

> Looks good to me, but I'm too unfamiliar with the macro expansion. @owenca can you provide feedback?

So am I, but I prefer that it be fixed there instead of in the unwrapped line formatter. Ping @r4nt, the author of the macro expander.

https://github.com/llvm/llvm-project/pull/204421