[clang] [Modules] Fix an identifier hiding a function-like macro definition. (PR #135471)

[Jan Svoboda via cfe-commits]

https://github.com/jansvoboda11 approved this pull request.

LGTM. The behavior is a bit subtle (always was), but it's good to have this edge-case fixed.

https://github.com/llvm/llvm-project/pull/135471