HPCC-9956 Fix build break in windows introduced by previous commit.

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>

system/jlib/jsocket.cpp

@@ -505,6 +505,7 @@ static win_socket_library ws32_lib;
 #define ENOTCONN WSAENOTCONN
 #define EWOULDBLOCK WSAEWOULDBLOCK
 #define EINPROGRESS WSAEINPROGRESS
+#define ENETUNREACH WSAENETUNREACH
 #define ENOTSOCK WSAENOTSOCK