Flag --incompatible_no_implicit_file_export will break Android Testing in Bazel 1.2.1

Incompatible flag --incompatible_no_implicit_file_export will break Android Testing once Bazel 1.2.1 is released.

Please see the following CI builds for more information:

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

Begin by reproducing the failures in the four linked Buildkite CI builds and inspect the Android testing samples; the issue names no source file or test. Done means the samples pass with --incompatible_no_implicit_file_export enabled and the relevant failure is resolved or documented.

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