Users can opt out and use the system-installed version with the
following configuration:
```
bundle:
terraform:
exec_path: terraform
```
This will find the binary in $PATH and replace it with the found value.
If this is not set, the initialize phase will install Terraform in the
bundle's cache directory.
This includes 3 mutators:
* Interpolate resources references to TF compatible format
* Convert resources struct to TF JSON format and write it to disk
* Run TF apply