[native assets] Use workspace pubspec for user-defines
Native assets are cached for the whole pub workspace. So to avoid
invalidating caches for running hooks from different root packages,
only read user-defines from the workspace `pubspec.yaml`.
Bug: https://github.com/dart-lang/native/issues/39
Bug: https://github.com/dart-lang/native/issues/2187
Change-Id: I3aeb91455a418004d3e28c231dc1f5d002c15739
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/+/422101
Auto-Submit: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Hossein Yousefi <yousefi@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Daco Harkes
e5d926da8c