Remove rustc_bitflags; use the bitflags crate

r? @alexcrichton

Run the miri test suite on the aux builder and travis

Reopen of #38350

see https://github.com/rust-lang/rust/pull/43340#issuecomment-316940762 for earlier discussion

Rationale for running miri's test suite in rustc's CI is that miri currently contains many features that we want in const eval in the future, and these features would break if the test suite is not run.

fixes #44077

r? @nikomatsakis

cc @EddyB

Refactor translation unit partitioning/collection as a query

This commit is targeted at #44486 with the ultimate goal of making the `collect_and_partition_translation_items` function a query. This mostly just involved query-ifying a few other systems along with plumbing the tcx instead of `SharedCrateContext` in a few locations.

Currently this only tackles the first bullet of #44486 and doesn't add a dedicated query for a particular codegen unit. I wasn't quite sure how to do that yet but figured this was good to put up.

Closes #44486

This commit moves the actual code generation in the compiler behind a query
keyed by a codegen unit's name. This ended up entailing quite a few internal
refactorings to enable this, along with a few cut corners:

* The `OutputFilenames` structure is now tracked in the `TyCtxt` as it affects a
  whole bunch of trans and such. This is now behind a query and threaded into
  the construction of the `TyCtxt`.

* The `TyCtxt` now has a channel "out the back" intended to send data to worker
  threads in rustc_trans. This is used as a sort of side effect of the codegen
  query but morally what's happening here is the return value of the query
  (currently unit but morally a path) is only valid once the background threads
  have all finished.

* Dispatching work items to the codegen threads was refactored to only rely on
  data in `TyCtxt`, which mostly just involved refactoring where data was
  stored, moving it from the translation thread to the controller thread's
  `CodegenContext` or the like.

* A new thread locals was introduced in trans to work around the query
  system. This is used in the implementation of `assert_module_sources` which
  looks like an artifact of the old query system and will presumably go away
  once red/green is up and running.

Fix some lints while I'm here.

rustbuild: Don't pass `-j` if called by `make`

In these situations Cargo just prints out a warning about ignoring the flag
anyway, so let `make` take care of jobs and whatnot instead of getting warnings
printed.

This commit attaches a channel to the LLVM workers to the `TyCtxt` which will
later be used during the codegen query to actually send work to LLVM workers.
Otherwise this commit is just plumbing this channel throughout the compiler to
ensure it reaches the right consumers.

This commit removes the `crate_trans_items` field from the `CrateContext` of
trans. This field, a big map, was calculated during partioning and was a set of
all translation items. This isn't quite incremental-friendly because the map may
change a lot but not have much effect on downstream consumers.

Instead a new query was added for the one location this map was needed, along
with a new comment explaining what the location is doing!

I believe this comment here is mostly talking about the `ptrcast` function call
below, so move the comment down to that block.

This is a big map that ends up inside of a `CrateContext` during translation for
all codegen units. This means that any change to the map may end up causing an
incremental recompilation of a codegen unit! In order to reduce the amount of
dependencies here between codegen units and the actual input crate this commit
refactors dealing with exported symbols and such into various queries.

The new queries are largely based on existing queries with filled out
implementations for the local crate in addition to external crates, but the main
idea is that while translating codegen untis no unit needs the entire set of
exported symbols, instead they only need queries about particulare `DefId`
instances every now and then.

The linking stage, however, still generates a full list of all exported symbols
from all crates, but that's going to always happen unconditionally anyway, so no
news there!

Otherwise we may emit double errors related to the `#[export_name]` attribute,
for example, and using a query should ensure that it's only emitted at most
once.

This commit moves the `collect_and_partition_translation_items` function into a
query on `TyCtxt` instead of a free function in trans, allowing us to track
dependencies and such of the function.

This commit moves the definition of the `ExportedSymbols` structure to the
`rustc` crate and then creates a query that'll be used to construct the
`ExportedSymbols` set. This in turn uses the reachablity query exposed in the
previous commit.

Turns out this was already set up as a query, just wasn't using it yet!

This commit refactors the the `partitioning::partition` function to operate with
a `TyCtxt` instead of a `SharedCrateContext` in preparation for making it a
query.

This commit refactors the `collect_crate_translation_items` function to only
require the `TyCtxt` instead of a `SharedCrateContext` in preparation for
query-ifying this portion of trans.

In these situations Cargo just prints out a warning about ignoring the flag
anyway, so let `make` take care of jobs and whatnot instead of getting warnings
printed.

Rollup of 17 pull requests

- Successful merges: #44073, #44088, #44381, #44397, #44509, #44533, #44549, #44553, #44562, #44567, #44595, #44604, #44617, #44622, #44630, #44639, #44647
- Failed merges:

Ensure tcp test case passes when disconnected from network

net::tcp::tests::connect_timeout_unroutable fails when the network
is unreachable, like on a laptop disconnected from wifi. Check for
this error and allow the test to pass.

Closes #44645

stabilized needs_drop (fixes #41890)

fixes #41890

compiletest: print the correct basename of the src dir

See <https://github.com/laumann/compiletest-rs/issues/76>.

Fixes #40712

Fix incorrect `into_inner` link in docs.

Fixes https://github.com/rust-lang/rust/issues/42373.

ci: Upload/download from a new S3 bucket

Moving buckets from us-east-1 to us-west-1 because us-west-1 is where
rust-central-station itself runs and in general is where we have all our other
buckets.

Update cargo submodule

Just a routine update

stabilized compiler_fences (fixes #41091)

I did not know what to proceed with "unstable-book" entry. The feature would no longer be unstable so I have deleted it. If it was the wrong call I'll revert it (unfortunately his case is not described in the CONTRIBUTING.md).

stabilized iterator_for_each (closes #42986)

Also updated clippy and rls as these use the iterator_for_each

I've made my first PR's today so most likely I've done something wrong. Sorry about that!

rustdoc: pretty-print Unevaluated expressions in types.

Fixes #44555.

r? @nikomatsakis

remove overzealous Box<ZeroSizeType> optimization

extend E0623 for earlybound and latebound for structs

This fixes #44508

r? @nikomatsakis

Add Rustfmt

r? @alexcrichton

Update compiler-builtins

~~I can't tell if this was ever used, but it's not used today.~~

See commits.