Fixing non Mac OS builds.

QGCExternalLibs.pri

@@ -292,5 +292,7 @@ contains (DEFINES, DISABLE_ZEROCONF) {
 } else:MacBuild|iOSBuild {
     message("Including support for Zeroconf (Bonjour)")
     DEFINES += QGC_ZEROCONF_ENABLED
+} else {
+    message("Skipping support for Zeroconf (unsupported platform)")
 }
 

src/comm/UDPLink.cc

@@ -77,7 +77,9 @@ static QString get_ip_address(const QString& address)
 UDPLink::UDPLink(UDPConfiguration* config)
     : _socket(NULL)
     , _connectState(false)
+    #if defined(QGC_ZEROCONF_ENABLED)
     , _dnssServiceRef(NULL)
+    #endif
 {
     Q_ASSERT(config != NULL);
     _config = config;

src/comm/UDPLink.h

@@ -205,9 +205,10 @@ private:
     bool _hardwareConnect();
     void _restartConnection();
 
-#if defined(QGC_ZEROCONF_ENABLED)
     void _registerZeroconf(uint16_t port, const std::string& regType);
     void _deregisterZeroconf();
+
+#if defined(QGC_ZEROCONF_ENABLED)
     DNSServiceRef  _dnssServiceRef;
 #endif