[Windows] Fixed regression when creating fallback fonts

In 3ccdeb4b58, we removed the
specialized multi font engine on Windows, causing us to go
through the same code path when loading fallbacks as on
other platforms.

When combined with 97f73e9577,
this caused an error, because the code in
QFontEngineMulti::loadEngine() only overrode the families
list, but not the singular family in the request. In the
QRawFont test, this would cause the requested fallback font
to correctly have "MS Shell Dlg2" as the only font in the
families list, but the request.family would still be
"QtBidiTestFont", the name of the main font. The singular family
in the request was preferred by the windows font database when
creating the LOGFONT. We would therefore load the latter for
the fallback as well and since it still does not support the
characters in question, we would continue searching.

Fixes: QTBUG-72836
Change-Id: I1787b57febcf6030d5c5b09bc2ef2c9558f05beb
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

src/gui/text/qfontengine.cpp

@@ -1842,7 +1842,8 @@ QFontEngine *QFontEngineMulti::loadEngine(int at)
 {
     QFontDef request(fontDef);
     request.styleStrategy |= QFont::NoFontMerging;
-    request.families = QStringList(fallbackFamilyAt(at - 1));
+    request.family = fallbackFamilyAt(at - 1);
+    request.families = QStringList(request.family);
 
     // At this point, the main script of the text has already been considered
     // when fetching the list of fallback families from the database, and the

tests/auto/gui/text/qrawfont/BLACKLIST

@@ -1,3 +0,0 @@
-# QTBUG-72836
-[unsupportedWritingSystem]
-windows