Foundation: initialize CFSocket on startup

Windows requires the networking subsystem (WinSock) to be initialized.
However, the user expects to be able to use the networking APIs in
Foundation without performing any one-time initialization.  Furthermore,
due to the macro usage in the initialization path, it is easier to
perform the initialization in C than in Swift.  CoreFoundation has a SPI
for this (`__CFSocketInitializeWinSock`).

Author: compnerd

CoreFoundation/Base.subproj/ForSwiftFoundationOnly.h

@@ -566,6 +566,10 @@ _stat_with_btime(const char *filename, struct stat *buffer, struct timespec *bti
 #warning "Enabling statx"
 #endif
 
+#if DEPLOYMENT_TARGET_WINDOWS
+CF_EXPORT void __CFSocketInitializeWinSock(void);
+#endif
+
 _CF_EXPORT_SCOPE_END
 
 #endif /* __COREFOUNDATION_FORSWIFTFOUNDATIONONLY__ */

Foundation/NSSwiftRuntime.swift

@@ -150,7 +150,10 @@ internal func __CFSwiftGetBaseClass() -> UnsafeRawPointer {
 @usableFromInline
 @_cdecl("__CFInitializeSwift")
 internal func __CFInitializeSwift() {
-    
+#if os(Windows)
+    __CFInitializeWinSock()
+#endif
+
     _CFRuntimeBridgeTypeToClass(CFStringGetTypeID(), unsafeBitCast(_NSCFString.self, to: UnsafeRawPointer.self))
     _CFRuntimeBridgeTypeToClass(CFArrayGetTypeID(), unsafeBitCast(_NSCFArray.self, to: UnsafeRawPointer.self))
     _CFRuntimeBridgeTypeToClass(CFDictionaryGetTypeID(), unsafeBitCast(_NSCFDictionary.self, to: UnsafeRawPointer.self))