chore(java11): use Java 11 to run Gradle (#8650)
chore(java11): use Java 11 to run Gradle (#8650)

The Spinnaker gradle plugin is compiled against Java 11, so we can't use Java 8 anymore. This uses the same OS to compile as the other Spinnaker projects.
ajordens/deck,ajordens/deck,spinnaker/deck,spinnaker/deck,ajordens/deck,spinnaker/deck,spinnaker/deck,ajordens/deck