Roll for https://github.com/dart-lang/native/issues/2187.
The `NativeAssetsBuildRunner` now checks the pubspec for valid
user-defines, errors if they are not valid, and loads them.
So, delete all code in dartdev which did this.
Change-Id: I34f5bba3f4a7c4847c9cd33901c2f0a2f915ea22
Cq-Include-Trybots: luci.dart.try:pkg-linux-debug-try,pkg-linux-release-arm64-try,pkg-linux-release-try,pkg-mac-release-arm64-try,pkg-win-release-arm64-try,pkg-mac-release-try,pkg-win-release-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/422720
Reviewed-by: Hossein Yousefi <yousefi@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Daco Harkes
6a74c59033