Making "Found In Build" a mandatory field

1. Open the Bug work item definition from Process Editor.
2. Select the "Workflow" tab
3. Double click the "New" state to open the "Work Flow State Field Rules" window

4. Click "New" and select "Microsoft.VSTS.Build.FoundIn"

4. Click "Rules" and select "Required". Save the work item definition.

5. Now "Found in Build" is added in the state diagram.

6. Once this is done, when creating a new defect, the user cannot save without entering the "found in build"