CMake: Fix CMP0058 warning when using Ninja
Summary:
CMake Warning (dev): Policy CMP0058 is not set: Ninja requires custom command byproducts to be explicit. Run "cmake --help-policy CMP0058" for policy details. Use the cmake_policy command to set the policy and suppress this warning. This project specifies custom command DEPENDS on files in the build tree that are not specified as the OUTPUT or BYPRODUCTS of any add_custom_command or add_custom_target: data/syntax-data.qrc
Reviewers: vkrause, dhaumann
Reviewed By: vkrause
Subscribers: Frameworks
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D6220