[clang] [clang][Modules] Complete the implementation of P2615: Meaningful exports (PR #194201)

[Victor Chernyakin via cfe-commits]

localspook wrote:

> A question, why did you implement this in Preprocessor? If I were going to implement this, I am going to implement this in Sema::ActOnFinishExportDecl in clang/lib/Sema/SemaModule.cpp

(I'm assuming you meant Parser instead of Preprocessor?) That's the easiest place I found to put the implementation so that it can be shared between `ExportDecl`s and `ExternSpecDecl`s. Putting it in `SemaModule.cpp` would be the better choice if we only cared about `ExportDecl`.


https://github.com/llvm/llvm-project/pull/194201