Flag --incompatible_disallow_empty_glob will break Bazel skylib in Bazel 1.2.1

[bazel-flag-bot]

Incompatible flag --incompatible_disallow_empty_glob will break Bazel skylib once Bazel 1.2.1 is released.

Please see the following CI builds for more information:

• [:windows: (OpenJDK 8)](:windows: (OpenJDK 8))
• [:ubuntu: 16.04 (OpenJDK 8)](:ubuntu: 16.04 (OpenJDK 8))
• [:ubuntu: 18.04 (OpenJDK 11)](:ubuntu: 18.04 (OpenJDK 11))
• [:darwin: (OpenJDK 8)](:darwin: (OpenJDK 8))

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.

[brandjon]

Flag flip tracked by bazelbuild/bazel#8195.

[limdor]

PR to make sure that there are no regressions in bazel-skylib. Once it is merged this issue could be closed https://github.com/bazelbuild/bazel-skylib/pull/447