Rebuild for QT 5.12.1 and updated to 5.19.13

Changelog:

• The sphinx extension now uses a single ref role.
• The default values arguments have reST references added if possible in the XML export.
• Added argument names and default values to the XML export.
• Restored the inclusion of reST references in the XML export.

Build python-qt5 against it which is a dep of calibre, which rebuilt fine and was working by installing