Gradle plugin builds to /buildSrc/build

I wrote my first Gradle plugin a bit ago, but I’m unable to publish it as whenever it builds, it creates a JAR with the structure:
|_gradle-plugins/
|_com.deflatedpickle.gradle.concurnas.properties
|_MANIFEST.MF

The file in gradle-plugins contains:
implementation-class=com.deflatedpickle.gradle.concurnas.Concurnas

And MANIFEST.MF contains:
Manifest-Version: 1.0

Now, I have noticed that in /buildSrc/build/ (as opposed to /build/), a JAR called buildSrc.jar is created with all of the sources included, but not the gradle-plugins folder.

One thing to note, is Gradle does warn that deprecated APIs are used when building. My thinking is that’s what’s wrong, but I’m not sure as it still builds elsewhere.

Am I just being dumb and missing a block to specify the output?

This is the full output of the build task.
It mentions being incompatible with Gradle 6, but I’'m building with Gradle 5.2.1.

My GitHub source!

Your source is likely in the incorrect location for what you’re trying to do. If you’re trying to publish a plugin that you can use in other projects, your plugin code should be what’s in src/main/groovy and src/main/java. The buildSrc/src/main/groovy and buildSrc/src/main/java are for plugins that you want to consume in the same project, not publish for use in other projects.

See https://docs.gradle.org/current/userguide/custom_plugins.html#sec:packaging_a_plugin for details.

I can’t believe it was that simple. Thank you for answering so nicely!