Improve test suite to include a more realistic suite of compiled programs

[thomcc]

There have been a few recent issues that should have been caught prior to release, and it's unfortunate that such a foundational crate in the ecosystem doesn't have better testing. Ideally, things like #754 and #747 would be caught before release, rather than learning about breakage after.

I think an option here would just be to snarf a few versions of popular -sys crates and compile them for a few targets that they support in CI. This is pretty optimistic, and in all practice I wouldn't be surprised if it ends up being somewhat more involved than this.