cmake: set nonancient minimum version

2.8.7 constantly prints a warning

CMakeLists.txt

@@ -26,7 +26,7 @@
 # STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 # THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-cmake_minimum_required(VERSION 2.8.7)
+cmake_minimum_required(VERSION 3.5)
 
 project(RandomX)