Copies of sources including only architecture independent binaries result in a failed-to-upload build

When a user copy a source and its binaries to another location and its binaries are all architecture independent, queue-builder gets confused and creates a new build record (non was necessary, since the binaries were copied too). The new build record will produce binaries that are already published and thus will fail-to-upload.

The new build should not be created, it involves a small fix in the way we treat arch-indep when looking up for builds (SPR.getBuildsByArch).