QtWidgets: Fix white text color on tabs on macOS for non-macOS styles

Apply white text only for macOS style.

Amends 2c0033983b

Task-number: QTBUG-59784
Change-Id: I9e66e929699efd715ed4565394f1aba763aeb32a
Reviewed-by: Jake Petroules <jake.petroules@qt.io>

src/widgets/widgets/qtabbar.cpp

@@ -176,12 +176,11 @@ void QTabBarPrivate::initBasicStyleOption(QStyleOptionTab *option, int tabIndex)
 
     if (tab.textColor.isValid())
         option->palette.setColor(q->foregroundRole(), tab.textColor);
-#ifdef Q_OS_MACOS
-    else if (isCurrent && !documentMode
+    else if (q->style()->inherits("QMacStyle")
+             && isCurrent && !documentMode
              && (QSysInfo::MacintoshVersion < QSysInfo::MV_10_10 || q->isActiveWindow())) {
         option->palette.setColor(QPalette::WindowText, Qt::white);
     }
-#endif
     option->icon = tab.icon;
     option->iconSize = q->iconSize();  // Will get the default value then.