Add a new function that returns the minimum CMake version required to
build Qt. Pass that value to cmake_minimum_required() when building
qtbase and its standalone tests.
The minimum supported CMake version is read from qtbase/.cmake.conf
and its value should be updated when the need arises. It's the main
source of truth for all repos.
Provide a way to lower the minimum CMake version at configure time by
passing a value via QT_FORCE_MIN_CMAKE_VERSION.
This is not an officially supported way of building Qt. If the
specified version is lower than Qt's supported minimum, show a
warning.
Nevertheless the option is useful for testing how Qt builds with a
different minimum CMake version due to different policies being
enabled by default.
Issue warnings for CMake versions that are higher than the minimum
version but are known to cause issues when building Qt.
A counterpart change is needed in qt5 to ensure the minimum CMake
version is set at the proper time for top-level builds.
Ideally we would use the same 'check the CMake minimum version` code
in all our repositories, but that will cause lots of duplication because
we can't really find_package() the code and doing something like
include(../qtbase/foo.cmake) hardcodes assumptions about repo
locations.
So for now we don't bump the minimum version in child repo
cmake_minimum_required calls (qtsvg, qtdeclarative, etc).
Instead we record both the minimum supported version and the computed
minimum version (in case a different version was forced) in
QtBuildInternalsExtra.cmake.
Then we require qtbase's computed min version in
qt_build_repo_begin().
This won't set policies as cmake_minimum_required would, but at least
it propagates what minimum CMake version should be used for child
repos.
We might still have to bump the versions in child repos at some point.
Task-number: QTBUG-88086
Change-Id: Ida1c0d5d3e0fbb15d2aee9b68abab7a1648774b9
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
72aab8b487