Posted on 23 April 2014
We’re aware of an issue with Steam’s latest client API, released on the 22nd of April, that is preventing external SDKs and build tools to be called resulting in failed iOS, Android, Windows Phone and Ubuntu builds amongst others.
We are looking to resolve this issue as quickly as possible with Valve, and will update the known issue at http://help.yoyogames.com/entries/50884976 the moment we have more information.
Until this issue is fixed we can only suggest putting off the Steam client update.
NB: This only affects the Steam version of GameMaker: Studio.
- The YoYo Team