Description of problem:
Many packages in Fedora are noarch (particularly those written in interpreted languages). Currently, if someone wants a package to appear in both the x86_64 and i686 repositories, it has to be built twice. This is a waste of builder time.
It should be possible for the COPR owner to specify that a particular build is "noarch" and that it should use only one builder and copy the results to both architecture repositories. This would free up more builders for other tasks.
With the recent transition to the new OpenStack instance and optimization of VM usage we could easily afford to build noarch package twice. Proposed approach isn't trivial to implement and it will complicate build process further.