Depends which version of Xcode you are using.
In 4.5 you can go into the build settings "Summary" tab and set this in the "Status Bar" section.
If you don't have 4.5 then in the build settings "Info" section add a plist entry for "Status Bar Is Initially Hidden" and set it to YES. (Alternatively, download Xcode 4.5 because you should do this anyway).
