Make the rust input packager aware of rmeta files.
Make the rust input packager aware of rmeta files.

Distributing rust compilations was failing routinely due to the
dependent crate discovery mechanism coming up empty looking for
rlibs passed with --extern. As or a recent rustc version rmeta files
are passed instead, so we need to take those into account.

mozilla/sccache,mozilla/sccache,glandium/sccache,glandium/sccache,luser/sccache2,glandium/sccache,luser/sccache2,luser/sccache2,mozilla/sccache,luser/sccache2,glandium/sccache