macOS: respect strikeout attribute in menu item fonts

When we draw menu item text with CoreText instead of QPainter, then we
need to translate QFont::strikeOut() explicitly to an entry in the
attribute dictionary.

Task-number: QTBUG-136215
Change-Id: Ic4a895cd10c950c477acffca0078718490f4f0b7
Reviewed-by: Tor Arne Vestbø <[email protected]>

Author: Maddimax

src/plugins/styles/mac/qmacstyle_mac.mm

@@ -4289,7 +4289,9 @@ static QPixmap darkenPixmap(const QPixmap &pixmap)
                             withAttributes:@{ NSFontAttributeName:f, NSForegroundColorAttributeName:c,
                                                 NSObliquenessAttributeName: [NSNumber numberWithDouble: myFont.italic() ? 0.3 : 0.0],
                                                 NSUnderlineStyleAttributeName: [NSNumber numberWithInt: myFont.underline() ? NSUnderlineStyleSingle
-                                                                                                                           : NSUnderlineStyleNone]}];
+                                                                                                                           : NSUnderlineStyleNone],
+                                                NSStrikethroughStyleAttributeName: [NSNumber numberWithInt: myFont.strikeOut() ? NSUnderlineStyleSingle
+                                                                                                                               : NSUnderlineStyleNone]}];
 
                     d->restoreNSGraphicsContext(cgCtx);
                 } else {