Import structopt-derive-0.4.7 am: dc6194e23f am: eac406d5f2 am: 8af416f386

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/structopt-derive/+/1322913

Change-Id: I40c660ee151d1f5355f2bff5a3330871de5f333a