Teach skydb about --release and --debug

Previously, skydb could be used only for Debug builds. As part of working on
graphics performance, I'd like to use it for release builds as well. This CL
teaches it to use the same configuration arguments as sky_server, test_sky, and
test_perf.

The downside of this CL is that you'll need to supply --debug in the common
case of working with a debug build.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/746473003