Remove option `--build-target` from `test/testrunner/testrunner.py`.

These days, the only supported way to build/test target configurations
defined in `test/testrunner/target_config.py` seems to be via script
`test/testrunner/run_build_test_target.py`.

The `--build-target` option of script `test/testrunner/testrunner.py`
does not seem to be used anywhere and creates some confusion with the
logic in script `test/testrunner/run_build_test_target.py`.

Test: Rely on `master-art-host` build/test targets.
Change-Id: Ib4ac6ae9ce4d04cb33f2fba04f2a180e45bce7f1
1 file changed