Building a gradle plugin with maven can be difficult task. This is a hybrid solution.

• only the build phase is delegated to Gradle
• dependencies must be declared in pom.xml
• Maven is copying over all declared dependencies (with transitive ones) to target/dependencies/compile folder
• Gradle is taking them from there
• Maven is in charge of deployment

• Refresh dependencies for Gradle project (in root folder): mvn -pl plugin-gradle -am clean compile
• First time import the project into IDE as gradle project (tested with IDEA, and Eclipse)
• Run tests mvn -pl plugin-gradle -am clean integration-test
• Publish plugin to local maven repository with (in root folder): mvn -DskipTests -pl plugin-gradle -am clean install

• i.e. in Eclipse, the imported project doesn't know the outside world, if changes applied to dependencies, they must be refreshed with maven
• sources are not accessible by default

Maybe a better solution exists, but this would require some more research.