[llvm] Sketch of build and code changes for llvm shared library build using explicit visibility annotations (PR #96630)

[Thomas Fransham via llvm-commits]

fsfod wrote:

> @fsfod, @compnerd, @tstellar, @rnk, what is the preferred way to move forward here? If we want atomic history we should probably land the whole pull request. It is not clear to me if we can chunk it at a reasonable level...

The thing a lot of these changes can't go in without the rest of changes in my full branch that annotates the whole llvm codebase headers with export macros and the many fixes required from MSVC instantiating all class members. People probably still want the old windows shared library build system to also keep working before all my changes are merged so the export macros on windows would initially have to be a nop.

What i was thinking was just get the export macros definitions and cmake machinery to drive them merged first.





https://github.com/llvm/llvm-project/pull/96630