[lld] [LLD][Cygwin] Add libcygwin to exclude from auto-export library list (PR #143118)

[Tomohiro Kashiwada via llvm-commits]

kikairoya wrote:

Added.
libmsys-2.0 is defined here: https://github.com/msys2/MSYS2-packages/blob/89f4fafd5c60944e95ded7fb025fd6ed17d53374/msys2-runtime/0003-Rename-dll-from-cygwin-to-msys.patch#L70-L77

https://github.com/llvm/llvm-project/pull/143118