Flutter web build exits with error due to Dart SDK

Support
8

I am using the master channel.
FLUTTER_BRANCH=grep channel: .metadata | sed 's/ channel: //g'
FLUTTER_REVISION=grep revision: .metadata | sed 's/ revision: //g'
…
git checkout $FLUTTER_BRANCH
git pull origin $FLUTTER_BRANCH
git checkout $FLUTTER_REVISION
…