Fix build failed on windows

Udp mux need retrieve destination address to dispatch received
packet when listen at Any address. Windows use winsock APIs to
get that, but conn.FD() is not implement for windows, so
dispatch packet to first candidate, not ideally, but it will
work for ice connectin, wasm will have same result too.

udp_mux.go

@@ -365,12 +365,19 @@ func (m *UDPMuxDefault) connWorker() { //nolint:gocognit
 		var destinationConn *udpMuxedConn
 		m.addressMapMu.Lock()
 		if conns, ok := m.addressMap[addr.String()]; ok {
-			destinationConn = conns[ipAddr(localHost.String())]
+			if localHost.IsUnspecified() {
+				for _, c := range conns {
+					destinationConn = c
+					break
+				}
+			} else {
+				destinationConn = conns[ipAddr(localHost.String())]
+			}
 		}
 		m.addressMapMu.Unlock()
 
 		// If we haven't seen this address before but is a STUN packet lookup by ufrag
-		if destinationConn == nil && stun.IsMessage(buf[:n]) {
+		if destinationConn == nil && stun.IsMessage(buf[:n]) && !localHost.IsUnspecified() {
 			msg := &stun.Message{
 				Raw: append([]byte{}, buf[:n]...),
 			}

udpmsghelper.go

@@ -1,4 +1,4 @@
-//go:build !js
+//go:build !js && !windows
 
 package ice
 

udpmsghelper_js_win.go

@@ -1,4 +1,4 @@
-//go:build js
+//go:build js || windows
 
 package ice