[macOS] QTabBar tab button must be retrieved with button position "QTabBar::ButtonPosition::LeftSide" when tab bar position is set to "QTabWidget::West"

On macOS, when a QTabBar is positioned vertically using "QTabWidget::West", accessing tab buttons using "QTabBar::ButtonPosition::RightSide" returns "nullptr" contrary to Linux and Windows.

A workaround is to use "QTabBar::ButtonPosition::LeftSide" instead of ""QTabBar::ButtonPosition::RightSide".

Here is an example of portable code for suppressing the close button of a tab widget :

QTabWidget* tab_widget = new QTabWidget(this);
tab_widget->addTab(new QWidget(), "");
tab_widget->setTabPosition(QTabWidget::West); QTabBar::ButtonPosition button_pos =
#ifdef __APPLE__
    QTabBar::LeftSide;
#else
    QTabBar::RightSide;
#endif
tab_widget->tabBar()->tabButton(0, button_pos)->deleteLater();
tab_widget->tabBar()->setTabButton(0, button_pos, nullptr);