This would partially resolve
fortanix/rust-sgx#31

When ran on Windows `cp` will follow symlink: `checkout/build/<target>/<stage>/lib/rustlib/src/rust`.
It points to `checkout` which means the test will get stuck in copying loop until there is no space left.

As rustc is permanently unstable. So marking every items
with unstable is essential useless.

This simplifies the definition for ARCH.

Note that this changes asmjs-unknown-emscripten ARCH to `wasm32`,
which reflects the actual target arch.

Simplifies some of the expressions, and provides a default.

This allows setting a default abort using the core intrinsic.

Use a fall-through for no_std targets.

The `lifetimes` field is always empty. This commit removes it, and
renames the type as `Bounds`.

…t scope

- Accept DefId in resolve_str_path_error

This will probably break lots of internal invariants.

This fixes a failure in stage2 rustdoc tests.

This includes both `macro_rules!` and proc-macros.

Trait implementations are treated the same as modules for the purposes
of intra-doc links.

intra_doc_resolution_failure is not a lint.

It's equivalent to `Ident::from_str_and_span`. The commit also
introduces some more static symbols so that `Ident::new` can be used in
various places instead of `Ident::from_str_and_span`.

The commit also changes `Path::path` from a `&str` to a `Symbol`, which
then allows the lifetime annotation to be removed from `Ty`. Also, the
use of `Symbol` in `Bounds` removes the need for its lifetime
annotation.

It's intended only for very temporary use.

This replaces the need for the `description` and `details` symbols in
`UnsafetyViolation`, which are static. As a result some
`Symbol::as_str()` calls are no longer necessary, which is nice.

…anishearth

Resolve items for cross-crate imports relative to the original module

~~Blocked on rust-lang#73103 and rust-lang#73566

Closes rust-lang#65983.

I tested on the following code (as mentioned in rust-lang#65983 (comment)):

```
pub use rand::Rng;
```
and rustdoc generated the following link: https://rust-random.github.io/rand/rand_core/trait.RngCore.html

…hrogb

Enable some timeouts in SGX platform

This would partially resolve fortanix/rust-sgx#31

cc @jethrogb and @Goirad

…atsakis

Fix MinGW `run-make-fulldeps` tests

`compiler-rt-works-on-mingw` and `libs-search-path` were not ran because `only-mingw` doesn't match any target.
Enabled and verified few ignored tests with `windows-gnu` toolchain. They are still ignored on MSVC since I'm not experienced with this target.

…Mark-Simulacrum

Add build support for Cargo's build-std feature.

This makes some changes to the standard library to make it easier to use with Cargo's build-std feature. The primary goal is to make it so that Cargo and its users do not need to know which crates to build and which features to use for every platform.

Conditional cfgs are adjusted so that there is usually a fall-through for unsupported platforms. Additionally, there is a "restricted-std" feature to mark `std` as unstable when used with build-std on no_std platforms. There is no intent to stabilize this feature for the foreseeable future.

This borrows some of the implementation for wasm which already does what this needs. More code sharing can be done with some other platforms (there is a lot of duplication with cloudabi, hermit, and sgx), but I figure that can be done in a future PR.

There are some small changes to stable behavior in this PR:
- `std::env::consts::ARCH` on asmjs now reports "wasm32", to match its actual architecture.
- Some of the wasm error messages for unsupported features report a slightly different error message so that the code can be reused.

There should otherwise not be any changes to how std is built for distribution via bootstrap.

This does not yet support all platforms when used with build-std.

- It doesn't work with 16-bit targets (hashbrown does not support that).
- It does not work with JSON spec targets.
    - In particular, all target triple snooping will need to be replaced with appropriate target option checking.
- Switching to gimli (rust-lang#73441) will make cross-building *much* easier.
- There are still a ton of issues on the Cargo side to resolve. A big one is panic strategy support.

Future PRs are intended to address some of these issues.

…er-warns, r=Mark-Simulacrum

Do not render unstable items for rustc doc

See the zulip conversion: https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/rustc.20doc.3A.20.22internal.20compiler.20API.22.20warns.20are.20everywhere!/near/203850782

Before:
![image](https://user-images.githubusercontent.com/15225902/87501971-9cff8780-c68a-11ea-93b4-ea53ce18a77b.png)
After:
![image](https://user-images.githubusercontent.com/15225902/87501985-a7218600-c68a-11ea-81c0-a6b5b120832c.png)

Nothing changes in unstable items of std:
Before:
![image](https://user-images.githubusercontent.com/15225902/87502004-b7d1fc00-c68a-11ea-9224-a27a1d2a81d6.png)
After:
![image](https://user-images.githubusercontent.com/15225902/87502018-c0c2cd80-c68a-11ea-9773-4c63158025cb.png)

Closes  rust-lang#54682

…ents, r=oli-obk

Some `Symbol` related improvements

These commits make things nicer and avoid some `Symbol::as_str()` calls.

r? @oli-obk

…rk-Simulacrum

Add CSS tidy check

r? @Mark-Simulacrum

… r=pietroalbini

Add RISC-V GNU/Linux to src/tools/build-manifest as a host platform

Missed during rust-lang#72973

…an-DPC

Clean up E0723 explanation

r? @Dylan-DPC