Support buildroot overrides #146
Description
It would be useful to be able to specify in our RPM git repo some packages to pin in the buildroot. This would allow us to e.g. temporarily work around bugs in newer versions of build tools.
Note in our use case, we're working with yum repos which keep older versions of packages, so they're available. But unlike e.g. Koji side tags, the packages of different versions are all in the same yum repo, so we can't just enable/disable yum repos at build time. Instead, we want the ability to specify non-latest NEVRAs.
One crude way to do this currently is via patching BuildRequires: in our spec files to pull in the desired version. But that complicates spec file maintenance.