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

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

Change-Id: I50da9fb579a1ac9964422a1b17a063a099bb25ae