[TRACKER] Qt6 transition

[thunder-coding]

How the transition should be done

Note: this section should be considered incomplete. I'll appreciate some changes suggested by people who have maintained Qt family in the past.

• Add Qt6 family of packages
• Initial migration of a few packages to link against Qt6
• Manual testing of the packages now linked against Qt6
  • addpkg(x11): qt6-*, bump(x11/feathernotes,featherpad,mkvtoolnix) #19464
• Complete transition to Qt6 for all packages that successfully link against it.
• Deprecate Qt5 family of packages, and finally remove it later

[xtkoba]

Just some remarks.

Qt 5.15.x is planned to reach EOL at 26th May 2023.

Qt 4.8.x reached EOL around 19th December 2015. On Gentoo (a GNU/Linux distribution), the last removal of Qt 4 components was taken took place on 7th August 2018, more than 2 years and a half after EOL. Obviously it is not at all easy to fulfill all the tasks.

[TomJo2000]

Marking the first 3 points as completed after the merger of

• addpkg(x11): qt6-*, bump(x11/feathernotes,featherpad,mkvtoolnix) #19464

Currently introduced qt6-* packages:

• 25ebf70 addpkg(x11): qt6-qtbase - truboxl
• 3fcd4c7 addpkg(x11): qt6-qtsvg - truboxl
• 13e74a0 addpkg(x11): qt6-shadertools - truboxl
• a9d9e17 addpkg(x11): qt6-qtmultimedia - truboxl
• f49aba3 addpkg(x11/qt6-qtlanguageserver): 6.7.1 - Biswa96
• c044c64 addpkg(x11/qt6-qtdeclarative): 6.7.1 - Biswa96
• 17ec89f addpkg(x11/qt6-qtcharts): 6.7.1 - Biswa96
• e51ef33 addpkg(x11/qt6-qtimageformats): 6.7.1 - Biswa96
• 4193ab3 addpkg(x11/qt6-qttools): 6.7.1 - Biswa96

Packages currently using Qt6:

• feathernotes
• featherpad
• mkvtoolnix

_{I will be updating this comment as more Qt6 packages are introduced}