This test runs the `Tests/QtAutogen/MocInclude` test inside symlinked
directories. The `MocInclude` test previously relied on
`get_filename_component(... REALPATH)` to get the real source tree
location and compute the path to `AutogenCoreTest.cmake` from it.
However, this does not work on Windows due to issue #17206. The
test has been passing on Windows only on machines where symlinks
cannot be created and the main part of the test is skipped. On
machines where symlinks can be created, the test failed with that
approach. Fix it by explicitly passing the path to the helper
script in as a cache entry. Avoid relying on `REALPATH`.
The minimum CMake version for Qt6 is 3.16, so all the calls to
cmake_minimum_required() are updated here to enforce that
minimum. This will avoid any CMake version-related warnings
from Qt.
Avoid hard-coding Qt5 where the tests could now be using
Qt5 or Qt6.
Fixes: #22188
Change the default value of `CMAKE_AUTOMOC_PATH_PREFIX` to `OFF` to
restore compatibility with behavior of CMake 3.15 and below.
C++ source files that are generated by Qt's meta object compiler (moc)
include the header file that was passed as input argument to moc. This
is usually a path relative to the source directory, for example
#include "../../source/dir/myobject.h"
That is problematic for reproducible builds as described in #18815.
To cope with that, the target property AUTOMOC_PATH_PREFIX was
introduced in CMake 3.16 by commit d018d27c10 (Autogen: Add moc path
prefix generation (AUTOMOC_PATH_PREFIX), 2019-09-13, v3.16.0-rc1~94^2~4).
The property is default-initialized from the variable
`CMAKE_AUTOMOC_PATH_PREFIX`, which defaults to `ON`.
If this property is ON, and myobject.h is located in an include
directory of the target, moc-generated C++ files include the file
without the "path prefix":
#include "myobject.h"
This behavior, however, can break projects that have equally named
header files in different include directories. As "not breaking
existing projects" trumps "have reproducible builds by default" we
change the default of `CMAKE_AUTOMOC_PATH_PREFIX` to `OFF`.
Also, it is now possible to pass `-DCMAKE_AUTOMOC_PATH_PREFIX=ON` on the
CMake command line. Before, it was overridden in `CMakeGenericSystem`.
Fixes: #20598
Issue: #18815
