TypeInstanceId

Summary:
Unique identifier of type.

For the following diff D47925430 for records, and plan to use later for enums.

Reviewed By: wendy728

Differential Revision: D47925429

fbshipit-source-id: 80bed3efaaed8b0abfff0a38a5b53041b4a6dcdb

Support coerced attrs value() and type

Summary:
You currently can't do anything with the `coerced_attr` except print them out. Let's implement the basic `type` and `value()` methods to work with coerced attrs, similar to how configured attrs has it.

Coerced attrs aren't really converted to `Value<'v>`s, which is why I think it's ok for this implementation to live in buck2_bxl crate, since that's the only place it would be used.

3 of the coerced attrs types (select, concat, and explicit configured dep) aren't well supported in this implementation, but let's at least support the majority of the coerced attrs for a first pass.

Reviewed By: scottcao

Differential Revision: D48323666

fbshipit-source-id: 16e93ed80b77d0d1804db5919547dd725e52d27a

buck2/oss: use custom %TEMP% in CircleCI on Windows (facebook#371)

Summary:
This helps to eliminate flakiness of doctests on Windows. Sometime they fail with:
```
error: couldn't create a temp dir: The system cannot find the path specified. (os error 3) at path "C:\\Users\\CIRCLE~1.PAC\\AppData\\Local\\Temp\\rustdoctest86bH8a\\rmetawkIVXG"
```

Probably something in CircleCI runner messes with default TEMP dir, causing rustc to fail with this error.

Tested on 15 reruns of CircleCI job, they all succeeded, so I'm pretty confident this helps, although not sure exactly why. Before that, at least few out of 5 were failing.

Pull Request resolved: facebook#371

Reviewed By: ndmitchell

Differential Revision: D47917932

fbshipit-source-id: 5d857e2f947e316e61f65764bb1f70b41bf275b8

rustc_action: always use LF line-endings

Summary: CRLF is a pain. Avoid it.

Reviewed By: shayne-fletcher

Differential Revision: D47553486

fbshipit-source-id: e137526acb72b429f5dd29ff31f30431363783d5

Simple refactor of prepare_cd_exe

Summary: Reduce duplication a little bit, make it easier to change things in the next diffs

Reviewed By: ianlevesque

Differential Revision: D47471859

fbshipit-source-id: 715a747cf8d3d0f29c02caa6c825323b0dbe2949

Label global

Summary: Can be used as type.

Reviewed By: ndmitchell

Differential Revision: D47163560

fbshipit-source-id: 73562cd6107af679cdbefca19bc818495c4baa1b