math/saga: Update to 9.12.4
With fix for continuing support for 'sdat' extension
(still in use by QGIS's qgis-processing-saga-nextgen plugin)
Changelog: https://sourceforge.net/p/saga-gis/wiki/Changelog%209.12.4/attachment/changelog_saga_9.12.4.txt
Reported by: portscout, Repology