Flag --incompatible_disable_depset_items will break Skydoc 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 Skydoc.

The flag is documented here: bazelbuild/bazel#9017

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

• Windows, OpenJDK 8
• Ubuntu 16.04, OpenJDK 8
• macOS, OpenJDK 8
• Ubuntu 18.04, OpenJDK 11

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

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