emulators/flexemu: Update to 3.30
- Change from autotools to cmake
- Change from Qt5 to Qt6
- Compiler needs C++17
- Preparations for test target (not buildable atm.)
Changelog: https://github.com/aladur/flexemu/commit/3b579e5014a2eb3a342b47c04047023cb9935a2b
Reported by: portscout, Repology