:farmer: sim6 windows CI: 13 warnings

[Crola1702]

Environment

• OS Version: Windows
• Source gz-sim6 build

Description

There are 13 warnings in gz_sim-ign-gazebo6-win

Steps to reproduce

1. Run a build in gz_sim-ign-gazebo6-win
2. See warnings appear

Output

Reference build: https://build.osrfoundation.org/job/gz_sim-ign-gazebo6-win/42/

Warnings (See attached hyperlinks for more details):

• 9 C4273: inconsistent dll linkage
• 1 C4834: discarding return value of function with 'nodiscard' attribute
• 3 C4584: 'ignition::physics::detail::ComposePlugin::type': base-class 'ignition::physics::detail::ComposePlugin::n,void>' is already a base-class of 'ignition::physics::detail::ComposePlugin::type'