Try out CFLAGS=-O0 for travis

Build passed in ~30 min, which is a big longer than the high 20s that I'm seeing in recent history. This implies that we use these libraries enough that optimizing them is worthwhile? Very dubious.

I thought that last week it was more like 40 minutes, and just barely scraping by under 50?

Anyhow, submitting this PR and closing immediately... for posterity?