Update to rustix 0.38

[chenx97]

This upgrade is meant to bring support for mips32r6 and mips64r6, two Tier-3 architectures that have recently got their own target_arch values.

[chenx97]

@eminence Do these changes look ok to you?

[chenx97]

@sunfishcode Does the upgrade look good to you?

[chenx97]

@eminence bitflags' minimum supported rust version is 1.56.0. What should we do now?

[chenx97]

like, announce 0.3.0 to break rust 1.48?

[chenx97]

... OMG rustix 0.38 now requires 1.63.0. I'll come back later...

[chenx97]

Just to provide some context, I'm proposing this upgrade because of this PR. @eminence any thoughts on the bump of MSRV?

[eminence]

Hrm. I'm finding it increasingly difficult to maintain old MSRVs, and there's very little guidance in the wider community about best practices.

rustix is such a foundational crate, it'll be brought into very many crate graphs, so I don't really want to stick with 0.37 forever, we'll need to upgrade to 0.38 at some point, even if that involves a MSRV bump.

So I'm thinking that we'll merge this now, but probably hold off on a release for a bit.

The change mentioned in #48 (comment) is probably big enough to warrant a bump to version 0.3.0, so the next terminal-size release will be 0.3.0

[chenx97]

Glad to know. Thanks.