[clang] Clang tooling generated visibility macros for Clang (PR #109702)

[Thomas Fransham via cfe-commits]

fsfod wrote:

If your stuck with having to include a class or function it in a public header there will be a macro you can add to it so the Clang tool skips adding visibility attributes added to it. At the file or folder level they can be excluded by adding them to the export config file used by the tool that would be stored in the include folder root.

https://github.com/llvm/llvm-project/pull/109702