Copy file after custom profile launch

Hi,
I would like to copy a file (steamclient.so) to the linux dedicated server version of our game. at the moment I do this manually. I build via Win64 Machine.
I think the PostBuildStep would be the right way to do this.

To add the following snippet to the uproject file does not seem to work.

,
	"PostBuildSteps":
	{
		"Linux": [
			"copy \"S:\\Company\\Builds\\steamclient.so\" \"S:\\Company\\Builds\\LinuxServer\\GameName\\Binaries\\Linux\\\"",
			"echo copied SteamClient.so successfully"
		]
	}

I also tried to add things to the LinuxServer.Target.cs, without success.

What should I try next?