Gradle configuration cache bug

Running ./gradlew myTask yields:

FAILURE: Build failed with an exception.

* What went wrong:
Could not load the value of field `provider` of `org.gradle.internal.serialize.codecs.core.ProviderBackedFileCollectionSpec` bean found in field `__specs__` of task `:myTask` of type `repro.MyTask`.
> null array

Change from:

org.gradle.configuration-cache=true

to:

org.gradle.configuration-cache=false

in gradle.properties and everything works fine.

Works in Kotlin?!

Now, checkout the cc/fixed branch. The only thing which is changed is that the tasks' spec property is set from Kotlin code instead of Java. The code is the same. Now, the build passes.