Once bug 1534533 is fixed, we can stop building geckodriver as part of the build job. Given that test jobs rely on the geckodriver binary as part of the common tests package, those will have to be updated first to be dependent on the
geckodriver-repack job instead.
Note that right now this job only runs for Nightly builds of Firefox, which will also change with bug 1534533. By then we will built it for every commit, but only sign the binaries for Nightly builds of Firefox.