Add `--no-build` (#358)
By default, we will build source distributions for both resolving and
installing, running arbitrary code. `--no-build` adds an option to ban
this and only install from wheels, no source distributions or git builds
allowed. We also don't fetch these and instead report immediately.
I've heard from users for whom this is a requirement, i'm implementing
it now because it's helpful for testing.
I'm thinking about adding a shared `PuffinSharedArgs` struct so we don't
have to repeat each option everywhere.
