Noticed when trying to upload a Kotlin Native library to Bintray that the version is created but there are no files. What is needed in a build.gradle.kts file to include the missing files?

I assume you're using the Bintray Gradle plugin—when using Kotlin multiplatform, you'll want to use the maven-publish plugin instead. If you need an example of a project that has a valid maven-publish configuration for Bintray and publishes native artifacts, you can check out my project https://gitlab.com/serebit/logkat.

Keep on getting a HTTP 404 from the Bintray server.

Maybe because https://github.com/gradle/gradle/issues/11412 still not fixed.

Yeah, there's a workaround in that issue.