I did another try.
On my system I had install gradle version 3.4.1 (configured with GRADLE_HOME).
When I ran the gradle script with it, it failed.
Moreover when the gradle wrapper was quite old the gradle.build.kts was full of red lines, and running the application lead to an error.
As soon as I updated the gradle on my machine to latest 4.2.1 all is fine in Idea, gradlew and gradle.
The version of gradle is extremely important. Try to use the latest one. Moreover I remembered I read somewhere that gradle v 4.0 have the issue you are currently facing.
I suppose you use the IntelliJ Idea 2016.1.x or recent.
Note: Even it is an warning I personally took it very seriously. Quite ofter idea warns the version of its kotlin plugin and project one (configured in gradle or maven) is not the same.
I noticed the latest kotlin dsl gradle DSL (built in the latest gradle - 4.2.1) comes with kotlin 1.1.50.
In my project on the github the gradle.build.kts based one is 1.1.51. Modify it to 1.1.50 and the warn should vanish.