run-libcore-tests.sh: check for tty

Have vogar suppress color related control characters if script output
is not to a tty. This is to ease reading logs from the bots.

Test: art/tools/run-libcore-tests.sh --mode host | tee /tmp/log.txt
Test: art/tools/run-libcore-tests.sh --mode host
Change-Id: I970647c6f5339090cae4af84402d4a70f2bfb031
1 file changed