Have the ART Buildbot and Golem generate timezones files in /system/etc/tz.

Have `tools/buildbot-build.sh --target` and Golem's target build
rule (`build-art-target-golem`) build targets `tzdata-art-test`,
`tzlookup.xml-art-test`, and `tz_version-art-test`, copying timezones
prebuilt files into /system/etc/tz, so that they can be found even if
the Runtime APEX is not available, by setting the environment variable
`ART_TEST_ANDROID_RUNTIME_ROOT` to "/system" on device.

This is a temporary change needed until the ART Buildbot fully
supports the Runtime APEX.

Test: Rely on the ART Buildbot and Golem.
Bug: 131667225
Bug: 121117762
Bug: 129332183
Bug: 119293618
Bug: 131239046
Change-Id: Ib9f748dea155b54eec0d000dd9e0f0dfb29ca626
2 files changed