Description of problem:
If I submit a new build with multiple SRPMs where there is a build dependency between two (or some) of them, Copr should build these in the correct order.

Version-Release number of selected component (if applicable):
Whatever is currently on https://copr.fedoraproject.org

How reproducible:
100%

Steps to Reproduce:
1. Create two SRPMs, foo and bar where foo takes longer to build than bar (to prevent racing from hiding the bug) and where bar has a BuildRequires on [the version of] the foo package.
2. Submit them both to Copr in a single build
3.

Actual results:
foo and bar will be built at the same time and bar will fail to build

Expected results:
foo should complete it's build before bar is started because bar depends on something in foo

Additional info:
An existing example of this is building evolution and evolution-ews.  The latter will typically fail because it depends on the same version of the former.