Upgrade rust/crates/structopt-derive to 0.4.15 am: 7081b4a371 am: 2aef36ce18 am: 517dacdb4f am: d3dbc4c419

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/structopt-derive/+/1791009

Change-Id: Icde8dccfb357199cb0bfae474ada2b4da4253e1e