Add --always-clean flag to run-test.

This flag makes run-test remove the test-artifacts even if it fails. Also
enable this option by default when doing run-tests with make. Add
a ART_TEST_RUN_TEST_ALWAYS_CLEAN environment variable to control this
option.

Change-Id: I7867b400d570d8d679d9822d1fa65f49eb3522ae
4 files changed