[llvm] [llvm] DLLExport public methods from SmallVector (PR #127850)

[Saleem Abdulrasool via llvm-commits]

compnerd wrote:

> The scope of the changes seems very broad to me, perhaps it would be worth reviving the discourse thread and making sure this is the direction we want to pursue?

Agreed, that the change is going to be very large in total, but scoping it to per-library is a reasonable approach IMO.

> Similarly, do we have a policy in place that will make us apply these macros in the future code?

Yes, @vgvassilev has a colleague who is looking into setting up [ids](https://github.com/compnerd/ids) to help catch missing annotations. I don't have the link for that conversation off hand unfortunately.

https://github.com/llvm/llvm-project/pull/127850