cmake warnings related to CMP0177 with cmake 3.31.0

[scpeters]

Environment

• OS Version: macOS 13.6.3-x86_64
• Source or binary build? source build of gz-plugin3 (gazebosim/gz-plugin@faaf65e) but appears to affect other versions as well, using binary version of gz-cmake4 4.1.0

Description

• Expected behavior: it should build with no cmake warnings
• Actual behavior: it has a cmake warning on macOS using the latest cmake 3.31.0 from homebrew

Steps to reproduce

1. Install cmake 3.31
2. Install gz-plugin dependencies
3. Configure gz-plugin
4. Observe warning

Output

https://build.osrfoundation.org/job/gz_plugin-ci-gz-plugin3-homebrew-amd64/21/cmake/

CMake Warning (dev) at /usr/local/share/cmake/gz-cmake4/cmake4/GzInstallAllHeaders.cmake:182 (install):
  Policy CMP0177 is not set: install() DESTINATION paths are normalized.  Run
  "cmake --help-policy CMP0177" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.
Call Stack (most recent call first):
  core/include/gz/plugin/CMakeLists.txt:1 (gz_install_all_headers)

Related: from cmake 3.31.0 release notes

The install() command's DESTINATION arguments are now normalized, with the exception of INCLUDES DESTINATION arguments in install(TARGETS). See policy CMP0177.

[scpeters]

I think we should try setting

if(POLICY CMP0177)
  cmake_policy(SET CMP0177 NEW)
endif()

and see if anything breaks