Update submodule sitl_gazebo to latest Fri Dec  4 00:39:14 UTC 2020
Update submodule sitl_gazebo to latest Fri Dec  4 00:39:14 UTC 2020

    - sitl_gazebo in PX4/Firmware (25c113a5273ab315c511773b23ef81e2a93f0026): https://github.com/PX4/PX4-SITL_gazebo/commit/cd8ba25c81f32d6fe088482e37f8a38892209ef4
    - sitl_gazebo current upstream: https://github.com/PX4/PX4-SITL_gazebo/commit/e01ba8f78c185fab0b0ceb1e6407b5e1cc7c07d4
    - Changes: https://github.com/PX4/PX4-SITL_gazebo/compare/cd8ba25c81f32d6fe088482e37f8a38892209ef4...e01ba8f78c185fab0b0ceb1e6407b5e1cc7c07d4

    e01ba8f 2020-12-03 JaeyoungLim - Add macos build tests for Bigsur (#663)
a6698f5 2020-11-19 Daniel Agar - update gitignore (#658)

krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,krbeverx/Firmware,krbeverx/Firmware