cmake: fix build with Qt 6.10

[Chiitoo]

The 'Qt6FooPrivate' targets have been split into separate CMake files
in Qt 6.9, and require a 'find_package(Qt6FooPrivate)' call starting
with Qt 6.10.

See also: https://bugreports.qt.io/browse/QTBUG-87776

[tsujan]

Thanks!

Any other library/app in addition to libfm-qt and lxqt-qtplugin?

[Chiitoo]

These are the only ones I initially bumped into on my regular install, which was missing at least lxqt-{admin,openssh-askpass,powermanagement,sudo} and xdg-desktop-portal-lxqt, from which only the last one seems to be needing the same treatment.

For applications, qps, qterminal, and screengrab at least seem to be OK.

[Chiitoo]

Hrm, thought I tested them out but... maybe not.

Some more:

• lximage-qt
• lxqt-panel
• pcmanfm-qt
• screengrab

(Maybe a tracker issue would have been nice for this, but o whell.)

[tsujan]

Please make PRs for all components that need them.

P.S.
I may not be available for some time but will come back.

[Chiitoo]

May take some time from now for me as well, but will do!

[tsujan]

May take some time from now for me as well

There's no rush at all; take your time. Thanks again for taking care of this!