This feature already exists. You can add shell commands to the end of builds by adding something like this to your .uproject file:
"PostBuildSteps":
{
"Win64": [
"copy $(ProjectDir)\Binaries\$(TargetPlatform)\$(TargetName).exe D:\SomeDir"
]
}
There’s a PreBuildSteps section too. Check out WriteCustomBuildStepScripts in UEBuildTarget.cs in UBT to see all the available variables.