[build] Add Windows optimization flags to dart_config
[build] Add Windows optimization flags to dart_config

Change-Id: I48afc0e286116b4473adfe2d4e884a68e5971f36
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/205000
Reviewed-by: Alexander Aprelev <dfb74c35a357c2059971a4bf7fe26b6a7c18085d@google.com>
Commit-Queue: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk