Make testrunner use an environment variable to control building.

If it sees ART_TEST_RUN_TEST_BUILD=true then it will build
dependencies before runnning tests by default.

Test: m clean && \
      ART_TEST_RUN_TEST_BUILD=false \
      ./test/testrunner/testrunner.py --verbose --host -j40 -b;
      # Observe that it calls make
Test: m clean && \
      ART_TEST_RUN_TEST_BUILD=true \
      ./test/testrunner/testrunner.py --verbose --host -j40 \
      --no-build-dependencies;
      # Observe that it does not call make
Test: m clean && \
      ART_TEST_RUN_TEST_BUILD=false\
      ./test/testrunner/testrunner.py --verbose --host -j40;
      # Observe that it does not call make
Test: m clean && \
      ART_TEST_RUN_TEST_BUILD=true \
      ./test/testrunner/testrunner.py --verbose --host -j40;
      # Observe that it calls make
Test: m clean && \
      ./test/testrunner/testrunner.py --verbose --host -j40;
      # Observe that it does not call make

Change-Id: Iedd9e5be42b0977b177c4c4e7f9a4805387d4535
2 files changed