It makes sense (in my opinion) to have the top-level CMakeLists.txt
to include and call certain commands that should be controlled by
qtbase, to avoid submodule update difficulties when we want to do
changes in qtbase that shouldn't concern the top-level file.
Create cmake/QtBaseTopLevelHelpers.cmake and move some pre-existing
code from the top-level CMakeLists.txt into separate functions that
are defined in qtbase.
This file will be included in the top-level one and said commands will
be called there.
This also prepares for qt_print_build_instructions not call
qt_internal_qt_configure_end anymore, because it will be called
by the top-level project.
Pick-to: 6.6
Change-Id: I1fe3490001cf441d742c64b2ef1f267cd4362f6a
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
