In IDE I click Project Structure -> Artefacts -...

# intellij

[hinst]

In IDE I click Project Structure -> Artefacts -> [+] -> JAR -> From modules -> module: project_main, Main Class: MainKt -> [v] Include in project build; then I click "Rebuild Project". Before that, I tried gradle jar .
Using IDE\Artefacts I get "no main manifest attribute"; Using gradle jar I get class-not-found kotlin.jvm.internal.Intrinsics