Enabling GKE Support

Enabling GKE support is done via the GKE feature flag by setting it to true. This can be done before running clusterctl init by using the EXP_CAPG_GKE environment variable:

export EXP_CAPG_GKE=true
clusterctl init --infrastructure gcp

IMPORTANT: To use GKE the service account used for CAPG will need the iam.serviceAccountTokenCreator role assigned.