Add ART_DEFAULT_COMPACT_DEX_LEVEL

If specified, this option changes the default compact dex level used
by dex2oat. Defaults to none currently.

Bug: 63756964
Test: ART_DEFAULT_COMPACT_DEX_LEVEL=fast mm test-art-host-gtest and verify it fails for now.
Test: test/testrunner/testrunner.py --host -j64 and verify it passes

Change-Id: Ib252f432b3545297725656a5cca40d1bb57b0ced
5 files changed