Enable new CMake policy to fix protobuf compilation

[Blast545]

Summary

This PR is actually a back port from main PR #1046, this will fix a build regression caused when using CMake versions older than 3.13.

This fix was merged in main, and this back port targets ign-gazebo3 aiming to be port forwarded up to ign-gazebo5 and address Windows CI build regressions there.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Signed-off-by: Jorge Perez jjperez@ekumenlabs.com

Note to maintainers: Remember to use Squash-Merge

[codecov]

Codecov Report

Merging #1059 (bd23527) into ign-gazebo3 (d9195c4) will increase coverage by 0.33%.
The diff coverage is 78.48%.

@@               Coverage Diff               @@
##           ign-gazebo3    #1059      +/-   ##
===============================================
+ Coverage        77.56%   77.90%   +0.33%     
===============================================
  Files              208      221      +13     
  Lines            11385    12687    +1302     
===============================================
+ Hits              8831     9884    +1053     
- Misses            2554     2803     +249     

Impacted Files	Coverage Δ
include/ignition/gazebo/EntityComponentManager.hh	100.00% <ø> (ø)
include/ignition/gazebo/Link.hh	100.00% <ø> (ø)
include/ignition/gazebo/Server.hh	100.00% <ø> (ø)
...nclude/ignition/gazebo/components/ContactSensor.hh	100.00% <ø> (ø)
include/ignition/gazebo/components/Factory.hh	96.05% <ø> (ø)
...nclude/ignition/gazebo/components/LogicalCamera.hh	100.00% <ø> (ø)
include/ignition/gazebo/components/Sensor.hh	100.00% <ø> (ø)
...nclude/ignition/gazebo/components/Serialization.hh	90.32% <ø> (ø)
include/ignition/gazebo/gui/GuiSystem.hh	0.00% <0.00%> (ø)
.../plugins/component_inspector/ComponentInspector.cc	8.58% <0.00%> (-0.90%)	⬇️
... and 124 more

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