Here is a quick tip to save time to those migrating their xcode3 project to xcode4:
If you get the message
No executable file specified.
Use the "file" or "exec-file" command. when trying to run your application, 2 solutions:
 Set LLDB as the debugger in your scheme edition panel, it works[/]
 OR Still use GDB, but fix it by creating the missing Info.plist file (check the fields that are created by the new project wizard or the Introjucer and adapt them). After creation you will also need to set the “Info.plist File” field in your Build settings to “Info.plist”.[/][/list]