Answer from the good folks at Microsoft is below and it works!. There are other property files like debugger_remote_windows.xml in the location ' C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V140\1033\'
IVCRulePropertyStorage rule = (IVCRulePropertyStorage)vcConfig.Rules.Item("WindowsRemoteDebugger");
rule.SetPropertyValue("RemoteDebuggerWorkingDirectory", "C:\\SomeWorkingDir\\");