[llvm] [llvm][Support] Add UNIX socket support (PR #73603)

[Michael Spencer via llvm-commits]

Bigcheese wrote:

> From what I understand, this makes binaries depending on Support, such as clang, now depend on winsock. That seems like an undesirable dependency in a compiler. Maybe this could live in its own library, instead of in Support? Then only tools that need unix sockets could depend on it.

I considered that a bit, but we already depend on stuff like shell32 and COM, and just linking to winsock doesn't really do anything, you have to actually call `WSAStartup` before it sets up anything.

If anyone actually encounters an issue with linking against winsock then it'd be fine with moving it, but I don't really see a point in doing that right now. Also note that clang itself will depend on this once https://github.com/llvm/llvm-project/pull/67562 lands. It was waiting on Windows support which is what this patch was for.

https://github.com/llvm/llvm-project/pull/73603