QT_TESTCASE_BUILDDIR was implicitly defined by Qt::Test target for
library users in Qt5. By default, this definition will point to
CMAKE_CURRENT_BINARY_DIR. This logic works similarly to qmake logic.
From user's perspective it might be useful to not rely on standard
search paths, but specify own. This can be done by setting the
QT_TESTCASE_BUILDDIR property for the user's target. CMake will
substute the value of the QT_TESTCASE_BUILDDIR property into the
QT_TESTCASE_BUILDDIR definition.
The implicit QT_TESTCASE_SOURCEDIR also seems to be useful. According
to the current logic, it points to CMAKE_CURRENT_SOURCE_DIR.
Fixes: QTBUG-92079
Change-Id: I8a9065f08e859c713b3c8cc08142a9ced0677770
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
70464b355e