Include QLocale::system() in matchingLocales() return list

QLocale::matchingLocales() only returns matches from the CLDR database,
it does not include the current system locale as a match, even if it
does match. Add the current system locale, if it matches.

Task-number: QTBUG-106644
Change-Id: If2e409bf0fd8582941646838330e36b79952d3f6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/text/qlocale.cpp

@@ -2748,6 +2748,15 @@ QList<QLocale> QLocale::matchingLocales(QLocale::Language language, QLocale::Scr
         ++index;
     }
 
+    // Add current system locale, if it matches
+    const auto syslocaledata = systemData();
+
+    if (filter.acceptLanguage(syslocaledata->m_language_id)) {
+        const QLocaleId id = syslocaledata->id();
+        if (filter.acceptScriptTerritory(id))
+            result.append(QLocale::system());
+    }
+
     return result;
 }