In #166783, I started a new release branch.

One component of making a release branch is pinning to a specific Dart commit SHA:

However, that will always cause the Linux licensing (engine) check to fail, because it references the Dart SHA:

The license test can only be run on a Linux machine, which most Flutter engineers do not use day-to-day, so they either need to remember (and use) a Linux machine, or they need to push, wait for the engine to build and for the license test to run (wasting resources otherwise), and copy the resulting Signature: ... in order to make progress.

The easiest thing to do would be able to regenerate the licenses golden on a Mac. @jtmcdole mentioned it might work now?

/cc @reidbaker