Finding cause of "Automatic Preferred Max Layout Width is not available on iOS versions prior to 8.0"

Here is one way to find the specific label that is causing this warning:

1. Right click on the warning and choose "Reveal in Log"
2. The warning in the log will be highlighted. Copy the interface builder object ID for this label (it looks like xxx-xx-xxx).
3. Paste this in the Find Navigator. When you click on this result it will open the interface builder with the offending label selected.

Running XCODE 6.1, I found the easiest way to do find the error was through the Report Navigator.

1. View -> Navigators -> Show Report Navigator or simply press ⌘-8
2. Click on the build in the left pane.
3. Click the details icon next to the warning.

4. Find the object id in the warning description.

5. Go to the file and search ⌘-f for the object id.

6. Fix the issue. Automatic Preferred Max Layout Width is not available on iOS versions prior to 8.0

As said in that post, you can also use this regex <label(?!.*preferredMaxLayoutWidth) in storyboard source to find all labels that do not have a preferredMaxLayoutWidth setted. Then correct it.