Build only the needed run-test shards with "test.py -b -t XXX"

This should make iteration on a single test much faster.

Note the buildbot-build.sh still does a proper full build,
however that can be disabled with --skip-run-tests-build .

Test: art/test.py -b -r --optimizing -t 001
Change-Id: I3bb261fd81227653426737132a4daefb9e3bbb02
7 files changed