This means moving the output path into SupplementaryOutputPaths, and
using the same sort of diagnostic dispatching that serialized
diagnostics use. This is part of what's needed to run the migrator
in batch mode.
Seeing Module<Args> is more likely to indicate some catastrophic
failure, for instance a missing type with the same name as the module,
than that we should remove the generic arguments.
rdar://problem/26639477
