Flag --incompatible_disable_depset_items will break rules_webtesting in a future Bazel release

[bazel-flag-bot]

Incompatible flag --incompatible_disable_depset_items will be enabled by default in a future Bazel release [1], thus breaking rules_webtesting.

The flag is documented here: https://github.com/bazelbuild/bazel/issues/9017

Please check the following CI builds for build and test results:

• macOS, OpenJDK 8
• Windows, OpenJDK 8
• Ubuntu 18.04, OpenJDK 11

Never heard of incompatible flags before? We have documentation that explains everything.

If you don't want to receive any future issues for rules_webtesting or if you have any questions, please file an issue in https://github.com/bazelbuild/continuous-integration

Important: Please do NOT modify the issue title since that might break our tools.

[1] The target release hasn't been determined yet. Our tool will update the issue title once the flag flip has been scheduled.