I did the following setting in the spock build. This was applied to the spock build after the the subprojects block that applies the sonar plugin and the allprojects block.

subprojects {
   sonar {
      serverUrl = 'http://localhost:9010'
   }
}

I checked that the sonar server was running under the above url. When running gradle sonar I got the following exception:

Caused by: java.io.FileNotFoundException: http://localhost:9000/deploy/jdbc-driver.jar