This cl applies the mixin transform only on the full dill. In addition,
this cl also adds a concatenate dills step to more closely match
modular builds in production.
Change-Id: Icb37c5e2180c9e8246334143a6f772a203f80bf9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/238320
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Joshua Litt <joshualitt@google.com>
