[llvm] [LLVM][Cygwin] add workaround for blocking connect/accept in AF_UNIX sockets (PR #140353)

[via llvm-commits]

jeremyd2019 wrote:

Does that work?  BTW, I couldn't find any users of `raw_socket_stream` grepping in llvm-project git worktree, except for the test.

https://github.com/llvm/llvm-project/pull/140353