[llvm] [TableGen] Add explicit symbol visibility macros to code generated (PR #107873)

[Thomas Fransham via llvm-commits]

fsfod wrote:

I would think so, but an in an offline chat with @compnerd he wondered why do we need to export this instead of clang and tests getting there own copy of the functions.

https://github.com/llvm/llvm-project/pull/107873