/usr/bin/env is the new canonical location of "env", use it. Change-Id: Ifc5fbd942d409b1f54057579c5f57ccac63d4b72
Use Fedora cloud images as the baseline for built disk images.
Overrides:
- To use a non-default URL for downloading base Fedora cloud images, use the environment variable DIB_CLOUD_IMAGES
- To download a non-default release of Fedora cloud images, use the environment variable DIB_RELEASE