Export .ipa for iOS App adhoc deployment

1. add testing device UDID to developer portal and download the updated provision profile
2. open project in XCode, select Product > Archive, it will create a .xcarchive
3. After the Archive operation completes, go to the Organizer, select your archive, select 
Distribute... > Save for Enterprise or Ad-Hoc Deployment
4. select an identity to sign it.
5. .ipa file created.

Ref: http://stackoverflow.com/questions/5265292/xcode-4-create-ipa-file-instead-of-xcarchive