CMake warning when EXTERNAL_PROPRIETARY flag is used

[dboltovskyi]

Bug Report

CMake warning is shown during SDL build when EXTERNAL_PROPRIETARY flag is used

Reproduction Steps

1. Build SDL in EXTERNAL_PROPRIETARY policy mode:

cmake ../sdl_core -DEXTENDED_POLICY=EXTERNAL_PROPRIETARY

Expected Behavior

No warning messages are displayed.

Observed Behavior

Warning message is shown:

CMake Warning (dev) at CMakeLists.txt:436 (add_dependencies):
  Policy CMP0046 is not set: Error on non-existent dependency in
  add_dependencies.  Run "cmake --help-policy CMP0046" for policy details.
  Use the cmake_policy command to set the policy and suppress this warning.

  The dependency target "copy_policy_library" of target "smartDeviceLinkCore"
  does not exist.
This warning is for project developers.  Use -Wno-dev to suppress it.

OS & Version Information

• OS/Version: Ubuntu 18.04
• SDL Core Version: https://github.com/smartdevicelink/sdl_core/tree/release/7.0.0 (3ec2b6b)
• Testing Against: N/A

Notes

Issue is not applicable for PROPRIETARY and HTTP policy modes

[jacobkeeler]

Closing with the merge of #3730