We want CAPI providers to be built and embedded in the installer binary when ART builds the installer with OSBS.

Currently CAPI providers are only built when the OPENSHIFT_INSTALL_CLUSTER_API env var is set for hack/build.sh. One way of resolving this would be to always build the providers, but gate the kas/etcd dependencies on the environment variable. Some prior art for that here: https://github.com/openshift/installer/pull/8273

The main issue with enabling CAPI provider builds will be the effect on build time, which is already long-running and somewhat unstable.