Temporary rollback from Ubuntu 18.04 to 16.04

We've already updated our Ubuntu stacks to 18.04, but as Gradle commands keep crashing, we'll rollback temporarily on Saturday.

If you run a build on the new Ubuntu 18.04 Ubuntu with a non-ASCII character in an environment variable, Gradle commands will crash. For example, if you use your favorite emoji: 🦄 , it fails. These could be other, more serious and more often used characters too, like vowels with accents (á or à) or Japanese characters, in the name of the git committer... These get sent to the build as an env, and that's it.

Example with the unicorn:

12:54:22.256 [DEBUG] [org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment] Configuring env variables: {PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/android-sdk-linux/tools:/opt/android-sdk-linux/tools/bin:/opt/android-sdk-linux/platform-tools, HOSTNAME=ec81a79c2337, TEST=🦄, OLDPWD=/proj, PWD=/proj, LANG=en_US.UTF-8, SHLVL=0, HOME=/root, ANDROID_HOME=/opt/android-sdk-linux}
----- End of the daemon log -----


FAILURE: Build failed with an exception.

* What went wrong:
Gradle build daemon disappeared unexpectedly (it may have been killed or may have crashed)

So we decided to roll back with the weekly stack update on Saturday (21 July). As soon as someone figures out the reason for this known Gradle issue and it gets fixed, we'll upgrade to 18.04 again.

Sorry for the inconvenience and happy building!