cmake: use new CMP0127 policy

cmake: use new CMP0127 policy

CMP0127 is a new policy introduced by CMake 3.22. without specifying
the policy, we'd have following warning when configuring the building
system using CMake 3.22:

CMake Warning (dev) at /usr/share/cmake-3.22/Modules/CMakeDependentOption.cmake:84 (message):
  Policy CMP0127 is not set: cmake_dependent_option() supports full Condition
  Syntax.  Run "cmake --help-policy CMP0127" for policy details.  Use the
  cmake_policy command to set the policy and suppress this warning.
Call Stack (most recent call first):
  CMakeLists.txt:255 (CMAKE_DEPENDENT_OPTION)
This warning is for project developers.  Use -Wno-dev to suppress it.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>