QTuioTouchPlugin fails to build with "Unix Makefiles" generator on macOS

Looks like there's some bug in upstream CMake when using the Unix Makefile generator on a macOS HFS case-insensitive filesystem.

Make fails with:

make[2]: *** No rule to make target `src/plugins/generic/tuiotouch/CMakeFiles/QTuioTouchPlugin.dir/depend'.  Stop.
make[1]: *** [src/plugins/generic/tuiotouch/CMakeFiles/QTuioTouchPlugin.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

On linux, there are 2 folders one called QTuioTouchPlugin.dir and another called qtuiotouchplugin.dir in the build dir, whereas on macOS there is only the mixed-case one, and files presumably get overridden / merged into the same folder and thus messes up the build.

Not 100% sure yet why there need to be 2 different dirs, but workaround is to use Ninja at the moment.

Upstream CMake issue: https://gitlab.kitware.com/cmake/cmake/-/issues/21915