Build fails if config directory is provided with closing backslash

[penpendede]

Issue occurred in guide4you repo but belongs here, seems to be Windows-specific

npm run build .\conf\simple\

fails while both

npm run build .\conf\simple

and

npm run build ./conf/simple/

work flawlessly. In principle that's no big deal but the tab completions of both cygwin's bash and powershell automatically add a terminal backslash.