Use TARGET_BUILD_UNBUNDLED in ART test builds.

This is the way to disable assumptions in the build system that a full
system image is to be built.

Test: rm -rf out && \
      art/test/testrunner/run_build_test_target.py art-linux-bionic-x64
Test: art/test/testrunner/testrunner.py --target --64 --optimizing && \
      art/tools/run-gtests.sh
  in test chroot on device
Test: art/tools/golem/build-target.sh --machine-type=android-armv8 --golem=art-jit
Bug: 157549171
Change-Id: I053d38985a9a840cac36cabc0bb5e1f945e9ca7f
4 files changed