Only use Unix sockets API under Unix in wxGTK.

wxGTK can now be used under Windows where Unix sockets are not available, add
a __UNIX__ preprocessor check.

Closes #14407.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71784 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/sockgtk.cpp

@@ -12,7 +12,7 @@
 // For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
-#if wxUSE_SOCKETS
+#if wxUSE_SOCKETS && defined(__UNIX__)
 
 #include "wx/apptrait.h"
 #include "wx/private/fdiomanager.h"
@@ -67,4 +67,4 @@ wxFDIOManager *wxGUIAppTraits::GetFDIOManager()
     return &s_manager;
 }
 
-#endif // wxUSE_SOCKETS
+#endif // wxUSE_SOCKETS && __UNIX__