webkit-efl: fix build with newer CMake 3.4 from oe-core

* cmake was upgraded in:
  commit 2a6e061712cfe9cb4738806a0c351a64e0d30144
  Author: Alexander Kanavin <alexander.kanavin@linux.intel.com>
  Date:   Fri Jan 22 15:37:32 2016 +0200

    cmake: update to 3.4.2

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>