Clang: Introduce DocumentParsed as job requirement

This is in prepration for a follow-up change, which introduces a state
where the Document is not yet parsed (it was reset) but the queue has
jobs.

All jobs get this requirement except those that generate an AST.

Change-Id: Ifcbb704e54108b40797180514c5ad3f3768ef10b
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/tools/clangbackend/source/clangtranslationunits.cpp

@@ -111,6 +111,13 @@ bool TranslationUnits::areAllTranslationUnitsParsed() const
     });
 }
 
+bool TranslationUnits::hasParsedTranslationUnit() const
+{
+    return Utils::anyOf(m_units, [](const TranslationUnitDataPtr &unit) {
+        return unit->parseTimePoint != TimePoint();
+    });
+}
+
 int TranslationUnits::size() const
 {
     return m_units.size();