I found this command which worked for me:
cordova build ios --device
cd platforms/ios/build/device
/usr/bin/xcrun -sdk iphoneos PackageApplication "$(pwd)/$PROJECT_NAME.app" -o "$(pwd)/$PROJECT_NAME.ipa"
Source: http://www.splinter.com.au/xcode-4-command-line-builds-of-iphone-apps/
I did run @MD. Mohiuddin Ahmed's Ruby script first, which would have changed my xcodeproj file. I'm not sure if that was necessary but I don't think so.
Update for XCode 8: As a commenter has noted, PackageApplication
has been removed from XCode 8. To update the process, see the question: What's the replacement for Xcode's PackageApplication?
Edited to clarify process by adding cordova build
command as suggested by comments.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…