[llvm] [Support][Windows] Add utility function for retrieving a DLL-exported function (PR #97905)

[Saleem Abdulrasool via llvm-commits]

compnerd wrote:

> FWIW, I continuously build and test LLVM (both running LLVM itself on, and generating code for) on 32 bit Windows targets, both i386 and arm.

In that case, I think that the suggestion is more a requirement - we cannot risk losing thee calling convention attribute on the function pointer.

https://github.com/llvm/llvm-project/pull/97905