CMake 3.20 breaks Qt-based projects using qt5_wrap_ui() command (ninja: error: dependency cycle: Project/Application_autogen -> ...)

Reproduced with CMake from master @ c0aa4244 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: 3a955035