Make all objects created by QtcProcess children of it

Sometimes after creating QtcProcess we move it into a different
thread. In this case we should move all the children, too.
Without parent-child relation all the children will stay in the
old thread.

Change-Id: Ibde44d6153092a155dd2d200a7116a046910dddc
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/libs/utils/processutils.h

@@ -54,7 +54,7 @@ private:
 class ProcessHelper : public QProcess
 {
 public:
-    ProcessHelper(QObject *parent = nullptr) : QProcess(parent)
+    ProcessHelper(QObject *parent) : QProcess(parent)
     {
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0) && defined(Q_OS_UNIX)
         setChildProcessModifier([this] { setupChildProcess_impl(); });