JitPack requires the Maven plugin

A couple days ago I was trying to help make a Java library available through JitPack, an adapter that acts as a Maven repository and builds artifacts from a Git code repository. The JitPack Gradle log seemed to say the build failed with an exception about not being able to find one of the plugins the project used. However, we eventually found that the further-up warning about the lack of maven plugin was much more important. Applying that fixed the problem and allowed the project to build.