CMake warnings: Policy CMP0175 is not set

[furgo16]

Parent issue: #161

The snap CMake build generates a number of these warnings:

  Policy CMP0175 is not set: add_custom_command() rejects invalid arguments.
  Run "cmake --help-policy CMP0175" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.
Call Stack (most recent call first):
  src/3rdParty/lazy_loader/CMakeLists.txt:10 (fc_copy_sources)
This warning is for project developers.  Use -Wno-dev to suppress it.

Impact

• Clogging log output (333 warnings)
• Does not seem to otherwise affect the build or the app at runtime.

Cause

Unknown

Solution

Unknown

Reference

1. TBD