Fix compilation with CMake 3.9

Signed-off-by: Łukasz Wojniłowicz <lukasz.wojnilowicz@gmail.com>
(cherry picked from commit 747762d138682be9abbe7307680013cd643da8cb)

1. Conflicts:
2. kmymoney/mymoney/CMakeLists.txt
3. kmymoney/mymoney/storage/tests/CMakeLists.txt
4. kmymoney/mymoney/tests/CMakeLists.txt

FIXED-IN:4.8.1
BUG:384258