Teach engine/src/sky/tools/gn and BUILD.gn files about --deploy mode #3263
Description
Let's start with Android. @johnmccutchan tells me that there is a PRODUCTION flag for Dart we could turn on as a simple first step. In later iterations we can add AOTC, etc.
@devoncarew will wire in the tool bits with #3262, hopefully @jason-simmons or @chinmaygarde are willing to do the script and GN changes.