There's been an uptick in the number of newly added JavaScript tests that aren't being tagged with "requires_replication" (or perhaps "requires_sharding" after the changes from da1e030 as part of SERVER-32052). Due to the changes from 8e5c10e as part of SERVER-33109, the mongod binary compiled by the Enterprise RHEL 6.2 build variant no longer supports --storageEngine=mobile. This makes the idea of SERVER-32223 to have burn_in_tests.py run with additional storage engine configurations on the Enterprise RHEL 6.2 build variant not viable for addressing the failures we'd see as a result of later running against the mobile storage engine (i.e. after the commit has been pushed).

We can instead define a new build variant for the mobile storage modeled off of the Enterprise RHEL 6.2 (mobile) build variant that exclusively runs the burn_in_tests task. It'll need to use --buildVariant=enterprise-rhel-62-64-bit-mobile in order to run newly added and modified tests under all of resmoke.py suite configurations the Enterprise RHEL 6.2 (mobile) would exercise. This approach has the advantage of ensuring tests which aren't correctly tagged with "requires_replication" or "requires_sharding" without needing to run the entire test suite against the mobile storage engine, thereby avoiding a steep increase in the makespan of a full patch build.

Note: The display name of the build variant will start with an exclamation point so it sorts to the top of list and it will also be added to the "required" Evergreen patch build alias.