cros-test: Install xz-utils for gscdevboard tast.

The gscqual archives are in .tar.xz archives which requires xz support
to extract.

BUG=b:562405995
TEST=None

Change-Id: I97da27eea952319a3f8bfe2f1a3cf620da3acf6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/8459385
Tested-by: Andrew Luo <aluo@chromium.org>
Reviewed-by: See Wai Fu <seewaifu@google.com>
Reviewed-by: Vadím Sukhomlínov <sukhomlinov@google.com>
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
Auto-Submit: Andrew Luo <aluo@chromium.org>
Commit-Queue: Andrew Luo <aluo@chromium.org>