you have a Mac PC with YosemiteOS but C2 run only on Windows, so let me understand, if you want to export for Mac from a Windows PC, via nw.js, i suggest to you use C3 directly from your Mac and export your nw.js game. Otherwise, always C3, from windows PC export via ".zip" file that don't affect files permissions, then copy and extract this zip into your Mac.
from what i have understand, export from Windows PC, from C2 for Mac it's impossible.