9cd5068854
sudo is not needed, since in-chroot elements are run in the context of the root user. Furthermore, sudo in pre-install is problematic as sudo may not have been installed yet (imagine a debootstrap build) Change-Id: Ib5c7e176a90fe3b8fa9c3cd702d3d815df54f472
Provide yum specific image building glue.
RHEL/Fedora/CentOS and other yum based distributions need specific yum customizations.
Customizations include caching of downloaded yum packages outside of the build chroot so that they can be reused by subsequent image builds. The cache increases image building speed when building multiple images, especially on slow connections. This is more effective than using an HTTP proxy as a yum cache since the same rpm from different mirrors is often requested.