[REVIEW-REQUEST] [CALCITE-4790] Make Gradle pass the 'user.timezone' to test JVM

[Alessandro Solimando <al...@gmail.com>]

Hello everyone,
can someone with some spare cycles check this 1 line PR:
https://github.com/apache/calcite/pull/2534

We all agree that tests must pass in all timezones, but since we have CI
jobs running in different timezones, it would be nice to be able to easily
test under the same conditions even locally, especially when working with
time-related data formats.

When recently debugging test failures related to tz, I had to
continuously cherry-pick this commit with the risk of leaving it there when
opening the final PR.

Note that we already support "user.language" and "user.country", so I think
there is no problem in expanding support to "user.timezone" as well.

Best regards,
Alessandro