Only download from remote when we absolutely have to

If the kit includes a correctly configured sysroot gdbserver will tell
us our hostPath. Respect that hostPath if it exists, otherwise fall back
to remote debug.

Also, populate the hostPath with the symbol file from the run
parameters.

Task-number: QTCREATORBUG-29614
Change-Id: I3838cd44aa96d7dfcd4ded660b8102a1532c5362
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/moduleshandler.cpp

@@ -273,9 +273,16 @@ void ModulesHandler::removeModule(const FilePath &modulePath)
         m_model->destroyItem(item);
 }
 
+static FilePath pickPath(const FilePath &hostPath, const FilePath &modulePath)
+{
+    if (!hostPath.isEmpty() && hostPath.exists())
+        return hostPath;
+    return modulePath; // Checking if this exists can be slow, delay it for as long as possible
+}
+
 void ModulesHandler::updateModule(const Module &module)
 {
-    const FilePath path = module.modulePath;
+    const FilePath path = pickPath(module.hostPath, module.modulePath);
     if (path.isEmpty())
         return;