Gradle Project: java.lang.NoClassDefFoundError: kotlin/jvm/internal/Intrinsics

Adding all project files to the jar fixed the problem for me. I added the following line to my build.gradle

jar {
    manifest {
        attributes ...
    }
    // This line of code recursively collects and copies all of a project's files
    // and adds them to the JAR itself. One can extend this task, to skip certain
    // files or particular types at will
    from { configurations.compileClasspath.collect { it.isDirectory() ? it : zipTree(it) } }
}

Update: Changed configurations.compile.collect to configurations.compileClasspath.collect according to this answer below.