Get more information when AstBuilder throws an exception

Change-Id: If095650e6e70efccdf6627f6007e70825ef81216
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/120240
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

Author: bwilkerson