Command line warning D9035: option 'Gm' has been deprecated and will be removed in a future release

Try selecting <inherit from parent or project defaults> for the Enable Minimal Rebuild option (under C/C++ > Code Generation). After this, the option should show No (/Gm-), not in bold. Make sure you do this for your project(s) (you could have several projects in the solution), and all property pages they inherit from.

I had the same problem using Visual Studio 2019, in the end the problem was in a second project I had in the same solution, that had the option set to Yes (/Gm).

According to the documentation

You may safely remove this option from your projects.

project property "Enable Minimal Rebuild" image

Configuration properties > C\C++ > Code Generation > set the Enable Minimal Rebuild to no,
and there is no warning.