This comit applies the following changes:

* Deletes the `is_allocator` query as it's no longer used
* Moves the `is_sanitizer_runtime` method to a query
* Moves the `is_profiler_runtime` method to a query
* Moves the `panic_strategy` method to a query
* Moves the `is_no_builtins` method to a query
* Deletes the cstore method of `is_compiler_builtins`. The query was added in
  #42588 but the `CrateStore` method was not deleted

A good bit of these methods were used late in linking during trans so a new
dedicated structure was created to ship a calculated form of this information
over to the linker rather than having to ship the whole of `TyCtxt` over to
linking.

[MIR] Restrict ProjectionElem::Index and Storage{Live,Dead} to Local.

(see #44285)

r? @nikomatsakis

Produce expansion info for more builtin macros

r? @jseyfried

fixes #43268

Compact display of static lib dependencies

Fixes #33173

Instead of displaying one dependency per line, I've changed the format to display them all in one line.

As a bonus they're in format of linker flags (`-lfoo`), so the output can be copy&pasted if one is actually going to link as suggested.

expand on using rustup custom toolchains in CONTRIBUTING.md

fixes #42484

Should i include more notes about how to use a local build *without* rustup? It can kinda feel like a cop-out otherwise. Other means that come to mind are setting `$RUSTC` directly and fully installing it.

cc @rust-lang/docs

Resync clippy to v0.0.156

None

rustbuild: Remove invalid doctest from bootstrap.py

add test for not optimized `pow` with constant power

Closes #34947

stabilize mem::discriminant (closes #24263)

rustc: Flag {i,u}128 as unsafe for FFI

These don't appear to have a stable ABI as noted in #41799 and the work in
compiler-builtins definitely seems to be confirming it!

More general `on_unimplemented`, with uses in `Try`

Allow `on_unimplemented` directives to specify both the label and the primary message of the trait error, and allow them to be controlled by flags - currently only to be desugaring-sensitive.

e.g.
```Rust
#[rustc_on_unimplemented(
    on(all(direct, from_desugaring="?"),
        message="the `?` operator can only be used in a \
        function that returns `Result` \
        (or another type that implements `{Try}`)",
        label="cannot use the `?` operator in a function that returns `{Self}`"),
)]
```

r? @nikomatsakis

rustc: rename CodeExtent to Scope and RegionMaps to ScopeTree.

r? @nikomatsakis

Maybe I should allow error messages to check the *specific* desugaring?
Thanks @huntiep for the idea!

Better StorageLive / StorageDead placement for constants.

Fixes problems in miri (see https://github.com/solson/miri/pull/324#issuecomment-326555552) caused by the new scope rules in #43932.
What I've tried to do here is always have a `StorageLive` but no `StorageDead` for `'static` slots.
It might not work perfectly in all cases, but it should unblock miri.

r? @nikomatsakis cc @oli-obk

rustc: Remove the `used_unsafe` field on TyCtxt

Now that lint levels are available for the entire compilation, this can be an
entirely local lint in `effect.rs`

cc #44137

Update rls

And expose the `CFG_VERSION` env var to tools so they can determine the version of Rust.

This gets the RLS back on master and so completes the PR dance for the generators PR.

r? @alexcrichton

Implement RFC 1925

cc #44101

powerpc64: improve extern struct ABI

These fixes all have to do with the 64-bit PowerPC ELF ABI for big-endian
targets.  The ELF v2 ABI for powerpc64le already worked well.

- Return after marking return aggregates indirect. Fixes #42757.
- Pass one-member float aggregates as direct argument values.
- Aggregate arguments less than 64-bit must be written in the least-
  significant bits of the parameter space.
- Larger aggregates are instead padded at the tail.
  (i.e. filling MSBs, padding the remaining LSBs.)

New tests were also added for the single-float aggregate, and a 3-byte
aggregate to check that it's filled into LSBs.  Overall, at least these
formerly-failing tests now pass on powerpc64:

- run-make/extern-fn-struct-passing-abi
- run-make/extern-fn-with-packed-struct
- run-pass/extern-pass-TwoU16s.rs
- run-pass/extern-pass-TwoU8s.rs
- run-pass/struct-return.rs

Add clippy as a submodule

~~This builds clippy as part of `./x.py build` (locally and in CI).~~

This allows building clippy with `./x.py build src/tools/clippy`

~~Needs https://github.com/nrc/dev-tools-team/issues/18#issuecomment-322456461 to be resolved before it can be merged.~~ Contributers can simply open a PR to clippy and point the submodule at the `pull/$pr_number/head` branch.

This does **not** build clippy or test the clippy test suite at all as per https://github.com/nrc/dev-tools-team/issues/18#issuecomment-321411418

r? @nrc

cc @Manishearth @llogiq @mcarton @alexcrichton

Closes #34947

Make sure that if the test is failed, the CI will stop the build.

Update cargo

This includes https://github.com/rust-lang/cargo/pull/4447 which fixes a bug in Cargo that is needed to fix https://github.com/rust-lang/rust/issues/44237.

r? @alexcrichton

Update html-diff-rs version

r? @nrc

add a lowercase suggestion to unknown_lints

I recently wrote some tests for a clippy lint, copied the (uppercase) lint name into my test file and forgot to toggle the case. This PR adds a suggestion that would have saved me 10 minutes of debugging, so it's likely a net win 🙂 . Also it adds a UI test for the `unknown_lints` lint.

These don't appear to have a stable ABI as noted in #41799 and the work in
compiler-builtins definitely seems to be confirming it!

This includes https://github.com/rust-lang/cargo/pull/4447 which fixes
a bug in Cargo that is needed to fix
https://github.com/rust-lang/rust/issues/44237.

Following Clang's lead, and anecdotal evidence from the `float_one` part
of `run-make/extern-fn-struct-passing-abi`, use a floating point
register to return single-float aggregates, except on MSVC targets.