As discussed today in Flutter Build Moot (#67373).

We had an idea to check-out the Dart SDK into two locations (i.e. one within flutter/third_party/dart, within the engine repo), and whatever work is required to start getting our own repository pointing to it, including possibly upstreaming configurable root directories or build overrides.

This issue is for @chinmaygarde and @jason-simmons to pair in the next ~2 weeks and land anything incremental they can, and list out any blockers or changes we'd need the Dart SDK to allow or implement.

Let's aim for Monday February 26th for the next update.