[llvm] [llvm] annotate interfaces in llvm/Support for DLL export (PR #136014)

[Andrew Rogers via llvm-commits]

andrurogerz wrote:

NOTE: this PR should not be merged until https://github.com/llvm/llvm-project/pull/135995 is merged or it will introduce warnings when LLVM is compiled with GCC.

https://github.com/llvm/llvm-project/pull/136014