Qt6 support

[cordlandwehr]

This is a work in progress parting state in relation to maliit/framework#125 .

Done:

• compile porting
• compiles with Qt6 & Qt5 version of Maliit

Next:

• adapt to coinstallable Maliit for Qt5 and Qt6
• runtime testing

[hedmo]

Following this. Added it on top of master . Both framework and keyboard compiled fine but the keyboard did not appear after reboot.

[JamiKettunen]

We also need a set(CMAKE_POSITION_INDEPENDENT_CODE ON) somewhere here just like in framework to prevent stuff like:

ld: error: relocation R_X86_64_PC32 cannot be used against symbol 'MaliitKeyboard::Logic::EventHandler::staticMetaObject'; recompile with -fPIC
>>> defined in libarplugin.so.lto.libmaliit-keyboard-lib.a(mocs_compilation.cpp.o at 31788).o
>>> referenced by moc_eventhandler.cpp:291 (maliit-keyboard-lib_autogen/LGVL4OH3BC/moc_eventhandler.cpp:291)
>>>               libarplugin.so.lto.libmaliit-keyboard-lib.a(eventhandler.cpp.o at 1370304).o:(MaliitKeyboard::Logic::EventHandler::onWordCandidatePressed(QString, bool))

[JamiKettunen]

After selecting this as my OSK in KDE Plasma 6 (Wayland) systemsettings I can already say that while holding spacebar for cursor selector works trying to use it by swiping on the empty area etc seems to just dismiss the keyboard when (accidentally) going past the very beginning/end of many UI textboxes like launcher and dolphin search. I may report back other oddities I see perhaps but these actually seem to be bugs on KDE side