CMake 3.20 breaks Qt-based projects using qt5_wrap_ui() command (ninja: error: dependency cycle: Project/Application_autogen -> ...)
Reproduced with CMake from master @ c0aa4244f5b1900c280b54a5453cc881dc7d3d95 on Ubuntu Linux.
Steps to reproduce:
* Clone https://github.com/KDAB/Charm.git
* Note: Needs qt5 dev environment + qtkeychain dev package (should be easy to install on a recent distro)
* Build the project, touch a file including a ui_*.h file, try to build again
See exact steps to reproduce + my output below:
```
% ninja clean
[2/2] Cleaning all built files...
Cleaning... 0 files.
% ~/opt/cmake-master/bin/cmake .
-- Building Charm 1.12.0-25-gfe99 in RelWithDebInfo mode
-- Qt5: Install Xcb headers and library for Xcb idle detection.
-- Charm will be installed to /home/kfunk/devel/install/master
-- The following OPTIONAL packages have been found:
* Git
* Qt5PrintSupport
-- The following REQUIRED packages have been found:
* Qt5Gui (required version >= 5.15.2)
* Qt5Widgets
* Qt5Xml
* Qt5Network
* Qt5Sql
* Qt5Test
* Qt5Core
* Qt5DBus
* Qt5Keychain, Provides support for secure credentials storage, <https://github.com/frankosterfeld/qtkeychain>
-- The following RECOMMENDED packages have not been found:
* XCB, Provides idle detection support for X11, <http://xcb.freedesktop.org>
-- Configuring done
-- Generating done
-- Build files have been written to: /home/kfunk/devel/build/kdab/Charm
% ninja
(...)
[178/178] Linking CXX executable Charm/charmtimetracker
=> WORKS
% ninja
ninja: no work to do.
% touch /home/kfunk/devel/src/kdab/Charm/Charm/Widgets/CharmPreferences.h
% ninja
(...)
[6/6] Linking CXX executable Charm/charmtimetracker
=> WORKS THE FIRST TIME
% ninja
ninja: error: dependency cycle: Charm/CharmApplication_autogen -> Charm/CMakeFiles/CharmApplication_autogen -> Charm/CharmApplication_autogen/timestamp -> Charm/ui_CharmPreferences.h -> Charm/CharmApplication_autogen
=> BREAKS ON SECOND TRY
```
This problem seems to be related to this new funcionality in CMake 3.20:
https://cmake.org/cmake/help/git-stage/policy/CMP0116.html
Reverting the following commit restores old behavior for me:
https://gitlab.kitware.com/cmake/cmake/-/commit/3a9550351200e6bfbda993b0ec3064bddb894b69
issue