Natron 2.6 w/ Qt 5 support (track progress)

[devernay]

This issue tracks Qt5 support progress, and replaces https://github.com/NatronGitHub/Natron/issues/256

Feel free to edit this issue, and use comments for discussion.

Target release

We will release 2.6 with Qt5.

Bugs introduced by Qt5

• https://github.com/NatronGitHub/Natron/issues/846

Checklist:

Natron GUI:

• [ ] File dialog
• [ ] NodeGraph
• [ ] Properties panels - affected by #846

OS Support

Windows

• [ ] Build (MinGW)
• [ ] Build (MSVC)
• [ ] Binary distribution

Linux

• [ ] Build (CentOS7+DTS11, docker image)
• [ ] Binary distribution (installer)
• [ ] Binary distribution (no installer)

macOS

• [X] Build (10.9) (Qt5 requires 10.12)
• [x] Build (10.15)
• [x] Build (12.x Intel)
• [x] Build (12.x M1)
• [x] Binary distribution (Intel)
• [x] Binary distribution (M1)

[rodlie]

So, are we going to distribute just qtbase or qt-everything?

[YakoYakoYokuYoku]

Preferably QtBase only for Windows and MacOS, otherwise for Linux QtWayland could be added too if we want support for Wayland, also I'm planning to make RB-2.6 compatible with Qt6, which also provides QtHttpServer.