Changes

[Sema] Introduce function reference conversion, NFC

Technically 'noexcept' isn't a qualifier, so this should be a separate conversion.

Also make the test a pure frontend test.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D67112

Build reproducible tarballs for releases

Currently the tarballs contain superfluous metadata, like the user name
of the packager and via Pax headers even the PID of the tar process that
packaged the files. We build the monorepo projects directly from the git
repo using "git archive" and for the test-suite we add some flags as
recommended by https://reproducible-builds.org/docs/archives/. We don't
use numeric owners though to be compatible with "git archive".

The advantage of "git archive" is that the releaser doesn't have to
download the tar ball and extract it, rather the archive is built
directly from the repository. This is probably what GitHub uses
internally to produce the tarballs, so I wouldn't expect a difference.

Reviewed By: tstellar

Differential Revision: https://reviews.llvm.org/D91494

[clangd] Introduce config parsing for External blocks

Enable configuration of remote and static indexes through config files
in addition to command line arguments.

Differential Revision: https://reviews.llvm.org/D90748

[clangd] Introduce config compilation for External blocks

Compilation logic for External blocks. A few of the high level points:
- Requires exactly one-of File/Server at a time:
  - Server is ignored in case of both, with a warning.
  - Having none is an error, would render ExternalBlock void.
- Ensures mountpoint is an absolute path:
  - Interprets it as relative to FragmentDirectory.
  - Defaults to FragmentDirectory when empty.
- Marks Background as Skip.

Depends on D90748.

Differential Revision: https://reviews.llvm.org/D90749

[clangd] Introduce ProjectAwareIndex

An index implementation that can dispatch to a variety of indexes
depending on the file path. Enables clangd to work with multiple indexes in the
same instance, configured via config files.

Depends on D90749, D90746

Differential Revision: https://reviews.llvm.org/D90750

[clangd] Use ProjectAwareIndex in ClangdMain

Put project-aware-index between command-line specified static index and
ClangdServer indexes.

This also moves remote-index dependency from clangDaemon to ClangdMain
in an attempt to prevent cyclic dependency between clangDaemon and
remote-index-marshalling.

Differential Revision: https://reviews.llvm.org/D91860

[clangd] Fix use-after-free in ProjectAwareIndex tests

[mlir][Python] Support finding pybind11 from the python environment.

* Makes `pip install pybind11` do the right thing with no further config.
* Since we now require a version of pybind11 greater than many LTS OS installs (>=2.6), a more convenient way to get a recent version is preferable.
* Also adds the version spec to find_package so it will skip older versions that may be lying around.
* Tested the full matrix of old system install, no system install, pip install and no pip install.

Differential Revision: https://reviews.llvm.org/D91903

[gn build] sort of merge 37ac559fccd4

It'd be nicer if there was a group target that forwarded either to
//clang-tools-extra/clangd/index/remote or
//clangd/index/remote/unimplemented based on if remote index is enabled,
but for now it's never enabled in the gn build.

[gn build] Port 067ffbfe601

[ARM] MVE VABD tests. NFC

[gn build] (manually) port ed424b428

[ARM] Ensure MVE_TwoOpPattern is used inside Predicate's

[Clang] Add __STDCPP_THREADS__ to standard predefine macros

According to https://eel.is/c++draft/cpp.predefined#2.6, `__STDCPP_THREADS__` is a predefined macro.

Differential Revision: https://reviews.llvm.org/D91747

[MLIR] ODS typedef gen fixes & improvements

- Fixes bug 48242 point 3 crash.
- Makes the improvments from points 1 & 2.

https://bugs.llvm.org/show_bug.cgi?id=48262

```
   def RTLValueType : Type<CPred<"isRTLValueType($_self)">, "Type"> {
     string cppType = "::mlir::Type";
   }
```
Works now, but merely by happenstance. Parameters expects a `TypeParameter` class def or a string representing a c++ type but doesn't enforce it.

Reviewed By: lattner

Differential Revision: https://reviews.llvm.org/D91939

[hwasan] Remove unused declaration shadowBase (NFC)

The function was introduced on Jan 23, 2019 in commit
73078ecd381b5ce95638c7a8e41fcabb6c27703a.

Its definition was removed on Oct 27, 2020 in commit
0930763b4baf926a39dd2d0571fd9e2102ec3831, leaving the declaration
unused.

[ValueMapper] Remove unused declaration remapFunction (NFC)

The function declaration with two parameters was introduced on Apr 16
2016 in commit f0d73f95c15f909c6034f1735632695248bb75a8 without a
corresponding definition.

[CodeGen] Use pred_empty (NFC)