When t7063 starts, it runs "update-index --untracked-cache"
to see if we support the untracked cache. Its output goes
straight to stderr, even if the test is not run with "-v".
Let's wrap it in a prereq that will hide the output by
default, but show it with "-v".
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>