get Duplicates Strategy
Returns the strategy to use when trying to copy more than one file to the same destination.
The value can be set with a case insensitive string of the enum value (e.g. 'exclude'} for DuplicatesStrategy#EXCLUDE).
This strategy can be overridden for individual files by using #eachFile(org.gradle.api.Action) or #filesMatching(String, org.gradle.api.Action).