Add ccache

[bthomee]

This change adds ccache to the Debian, Ubuntu, and RHEL images, so our CI pipelines can take advantage of caching (once configured to do so).

Note that due to our use of the UBI images of RHEL, the ccache package cannot be installed using the default repositories available through the package manager. I first tried installing it by pulling it from from GitHub, however that required installing an appropriate versioning for each RHEL distro as otherwise GLIBC incompatibilities would surface. Instead, I added the RHEL version-specific Fedora EPEL repository, which is a project that provides RHEL-compatible packages, as that will install a compatible ccache version.

To get a better view of which version is installed of which package, including ccache, they are now printed together at the end of each base image. This also acts as a sanity-check that the packages are actually installed.