Use ART image for make-based preopt.

Test: taimen-userdebug boots when built with
      DEXPREOPT_USE_ART_IMAGE=true
Test: Check logcat for checksum verification failures.
      (Build ART with extra logging in OatFileAssistant.)
Test: Check that bootclasspath-checksums from some prebuilt
      oat files contain only one image checksum followed by
      dex file checksums with
          grep -az -A1 -E '^bootclasspath-checksums$' <oat-file> | \
          xargs -0 echo | gawk '{print $2}'
Bug: 119800099
Change-Id: I241b65d7323901906ffcde91ca9ba173e1755ad7