STT: Generate output result from the test builds

Enable multiple test builds in one command and collect the results
from the build.trace.gz files.

Bug: 284915566
Test: combined_build_test.sh -t cf_x86_64_phone -v userdebug \
                     -d out/dist -a cf_x86_64_foldable -o -c droid
Change-Id: Ie566fd76463aa615c37130f4c4c7b8287fd8c447
2 files changed