Windows Phone Migration with Facebook Unity SDK

Hi, i have been migrating my game, its currently ruining on desktops, web and iOs, its a multiplayer socket social game, using the facebook SDK for unity.

the problem: Assests/facebook (facebook sdk folder) contains a DLL thats make the unity post builder throw an exception, this dll uses classes that don't have on windows phone platform, i tried to move this dll to specific targets folders, and get scripts erros

the question: how can i put this entire folder to be ignored by the unity compiler?

for now, im just deleting this folder and compiling tho WP, reinstall facebokk sdk and compile web/iOs ... its a workaround, and a pain

ty