Add cranelift-object

[philipc]

Fixes #761

[sunfishcode]

This looks really nice!

I attempted to update the crate versions to fix the CI, however we have a target-lexicon version conflict. I submitted gimli-rs/object#126 to update object to match the version currently used in cranelift. Once that's straightened out, this looks good to go!

[philipc]

I'll make a new object release and update this PR once gimli-rs/object#127 is sorted.

[bnjbvr]

(Please don't add merge commits to PRs, if that's possible. We've been trying really hard to have a linear history, and to rebase everything on top of previous work, so as to avoid merge commits and make bisection trivial. It's a small price to pay off for better debugging.)

[philipc]

When I rebase, should I squash 38d0289 so that the history is bisectable?

[bnjbvr]

Ideally, commits would be atomic, do one thing and keep on passing all the tests (that's really best effort, compared to the strong requirement of not having merge commits). If this matches this criteria, it's fine to keep it separated in my opinion. (We should probably agree on these conventions and put them in the CONTRIBUTING.md file at some point.)

[philipc]

CONTRIBUTING.md actually does pretty much say that already :)

[philipc]

Rebased and squashed.

[sunfishcode]

Thanks!