Fix miri imports for inclusion in libstd

[Aaron1011]

No description provided.

[RalfJung]

This blocks fixing the Miri component, would be good to get it landed ASAP. :)

[alexcrichton]

If you'd like to ensure that this continues to work over time you can add another thing to test here

[Aaron1011]

@alexcrichton: There's some additional work needed to get tests passing under Miri - I plan to open a follow-up PR.

[alexcrichton]

Oh it's also fine to just test a build, no need to run tests just yet if they don't work.

[Aaron1011]

@alexcrichton: I've addressed your comment. If it's okay with you, I'd like to do any CI changes in a follow-up PR, so that we get Miri building again quickly.

[alexcrichton]

👍

[Aaron1011]

@alexcrichton: Do we need to make a new release before bumping the submodule in rustc?

[alexcrichton]

I believe it's just a submodule update, so no a release isn't needed.