Custom build override for stable version check no longer needed

src/api/QGCCorePlugin.cc

@@ -303,3 +303,13 @@ bool QGCCorePlugin::guidedActionsControllerLogging(void) const
 {
     return GuidedActionsControllerLog().isDebugEnabled();
 }
+
+QString QGCCorePlugin::stableVersionCheckFileUrl(void) const
+{
+#ifdef QGC_CUSTOM_BUILD
+    // Custom builds must override to turn on and provide their own location
+    return QString();
+#else
+    return QString("https://s3-us-west-2.amazonaws.com/qgroundcontrol/latest/QGC.version.txt");
+#endif
+}

src/api/QGCCorePlugin.h

@@ -113,15 +113,16 @@ public:
     virtual QmlObjectListModel* customMapItems(void);
 
     /// Returns the url to download the stable version check file. Return QString() to indicate no version check should be performed.
-    /// Default implemenentation returns QGC Stable file location. Custom builds must override to turn off or provide their own location.
+    /// Default QGC mainline implemenentation returns QGC Stable file location. Default QGC custom build code returns QString().
+    /// Custom builds can override to turn on and provide their own location.
     /// The contents of this file should be a single line in the form:
     ///     v3.4.4
     /// This indicates the latest stable version number.
-    virtual QString stableVersionCheckFileUrl(void) { return QString("https://s3-us-west-2.amazonaws.com/qgroundcontrol/latest/QGC.version.txt"); }
+    virtual QString stableVersionCheckFileUrl(void) const;
 
     /// Returns the user visible url to show user where to download new stable builds from.
     /// Custom builds must override to provide their own location.
-    virtual QString stableDownloadLocation(void) { return QString("qgroundcontrol.com"); }
+    virtual QString stableDownloadLocation(void) const { return QString("qgroundcontrol.com"); }
 
     bool showTouchAreas(void) const { return _showTouchAreas; }
     bool showAdvancedUI(void) const { return _showAdvancedUI; }