[clang] [C++20] [Modules] Fix may-be incorrect ADL for module local entities (PR #123931)

[Nikita Popov via cfe-commits]

nikic wrote:

I'm not seeing any impact: https://llvm-compile-time-tracker.com/compare.php?from=ff0f1dd341cb2fdc1281a14413b3aa93bf9a20c7&to=4bfdd091675b9957686ac81457629e124950dc25&stat=instructions:u

https://github.com/llvm/llvm-project/pull/123931