OpenShift v4 Bare Metal IPI installer fails with Terraform provider errors

Issue

A baremetal IPI install for OpenShift v4.x fails with the following error:

DEBUG Initializing modules...
DEBUG
DEBUG Initializing the backend...
DEBUG
DEBUG Initializing provider plugins...
ERROR
ERROR Missing required providers.
ERROR
ERROR The following provider constraints are not met by the currently-installed
ERROR provider plugins:
ERROR
ERROR * ironic (any version)
ERROR * libvirt (any version)
ERROR
ERROR Terraform can automatically download and install plugins to meet the given
ERROR constraints, but this step was skipped due to the use of -get-plugins=false
ERROR and/or -plugin-dir on the command line.
ERROR
ERROR If automatic installation is not possible or desirable in your environment,
ERROR you may manually install plugins by downloading a suitable distribution package
ERROR and placing the plugin's executable file in one of the directories given in
ERROR by -plugin-dir on the command line, or in the following directory if custom
ERROR plugin directories are not set:
ERROR     terraform.d/plugins/linux_amd64
ERROR
ERROR
ERROR Error: missing provider "ironic"
ERROR
ERROR
ERROR
ERROR Error: missing provider "libvirt"
ERROR
ERROR
FATAL failed to fetch Cluster: failed to generate asset "Cluster": failed to create cluster: failed to initialize Terraform