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

[Nico Weber via llvm-commits]

nico 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.

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