The standalone compiler jar has been blown up since 5.1 due to the mass of more dependencies. We don't want to deploy such an "UBER" jar to Maven Central any longer.
Furthermore, building this standalone jar significantly slows down the compilation.
Instead, we'll put building it to a Maven profile. Whoever needs it will be able to build the standalone compiler jar by activating this profile in his/her local build.
In future, activate the profile build-standalone-jar in your local build to produce the standalone compiler jar, for instance: