You can add another classpath entry by creating an instance of org.gradle.plugins.ide.eclipse.model.Container:
eclipse {
classpath {
file {
whenMerged { classpath ->
def groovySupportContainer = new org.gradle.plugins.ide.eclipse.model.Container('GROOVY_SUPPORT')
groovySupportContainer.exported = true
classpath.entries << groovySupportContainer
}
}
}
}