[clang] [Clang] Apply exclude_from_explicit_instantiation to dllimport/dllexport (PR #168171)

[Hans Wennborg via cfe-commits]

zmodem wrote:

> If I remember correctly, there are a number of preexisting references to the problem that `exclude_from_explicit_instantiation` doesn't do what it would need to do on Windows; I think such references may exist in libcxx (in the code tree maybe?) and/or as other issues here on github. It would be a nice extra if we could find some of those references, to get more stakeholders aware of this change here (and possibly know which references to update).

I think the main one is https://github.com/llvm/llvm-project/issues/40363 maybe. It would be good to check how this interacts with the problem described there.

https://github.com/llvm/llvm-project/pull/168171