Current state of affairs with Foundation on Windows

Relates to: Windows Nightlies - #81 by abesmon
Strange things here :/

As I can see in code <fts.h> only includes when not DEPLOYMENT_TARGET_WINDOWS, but as error says, it's trying to include. I'm not sure, where from this variable come from. Must I provided it while building Foundation, or is it somehow comes from system. And if so, why it's trying to include on windows?