Warning during publish: 'Maven publication 'pluginMaven' pom metadata warnings'

Full warning:

```
> Task :pkl-gradle:generatePomFileForPluginMavenPublication
Maven publication 'pluginMaven' pom metadata warnings (silence with 'suppressPomMetadataWarningsFor(variant)'):
  - Variant runtimeElements:
      -  contains dependencies that cannot be represented in a published pom file.
          - dependency on project ':pkl-tools' declared with Gradle attributes
```