cmake build with qt6 (macos) does not include "plugins"

[Pavel Sanda]

On Tue, Mar 19, 2024 at 04:02:34PM +0100, pdv wrote:
> These steps have been added to my previous patch (new patch included) and I
> also derived the QT_PLUGINS_DIR and QT_LIBRARY_DIRS variables from the
> existing Qt6_DIR/Qt5_DIR variable, so they must not longer be supplied.

I see there is some very old bug related to osx budles, pehaps it should be closed?
https://www.lyx.org/trac/ticket/9018

> I only tested this with Qt6.

Unf we are staying out of Qt6 for mac because of serious issues we were not able to solve
(see bug https://www.lyx.org/trac/ticket/12641 ).

Pavel