Error with Qt 6 and autotools

[Cor Blom]

> [   45s] make  all-am [   45s] make[6]: Entering directory
> '/home/abuild/rpmbuild/BUILD/lyx-qt6-2.4.1692654261.fe74c24da9/src/frontends/qt'
>
> [   45s]   CXX      ButtonPolicy.o
> [   45s]   CXX      Dialog.o [   45s]   CXX      DialogFactory.o [
> 45s]   CXX      Action.o [   45s] In file included from
> Dialog.cpp:15: [   45s] GuiView.h:22:10: fatal error: QMainWindow: No
> such file or directory [   45s]    22 | #include <QMainWindow> [
> 45s]       |          ^~~~~~~~~~~~~ [   45s] compilation terminated. 
> [   45s] make[6]: *** [Makefile:1015: Dialog.o] Error 1 [   45s]
> make[6]: *** Waiting for unfinished jobs.... [   45s] In file
> included from FindAndReplace.h:15, [   45s]                  from
> DialogFactory.cpp:14: [   45s] DockView.h:17:10: fatal error:
> QDockWidget: No such file or directory [   45s]    17 | #include
> <QDockWidget> [   45s]       |          ^~~~~~~~~~~~~ [   45s]
> compilation terminated. [   45s] make[6]: *** [Makefile:1015:
> DialogFactory.o] Error 1 [   45s] In file included from
> Action.cpp:14: [   45s] GuiApplication.h:21:10: fatal error:
> QApplication: No such file or directory [   45s]    21 | #include
> <QApplication> [   45s]       |          ^~~~~~~~~~~~~~ [   45s]
> compilation terminated.

I tried something, looking at what could not be found. Those files are
not immediately under /usr/include/qt6 but in their respective
subfolders: QtConcurrent, QtWidgets, QtSvg and QtSvgWidgets. So I linked
the content of those folders to /usr/include/qt6 The result is that
compilation passes the place of the error above. (Later there is an
error, but I assume this has to do with my messing with the files.)

In CMakeLists.text there is the following line, which possibly makes it
work with cmake:

if(Qt6Core_FOUND)
        qt_use_modules(frontend_qt Core Gui Widgets Concurrent Svg
SvgWidgets)

Maybe this helps?

Cor