On a few compilers (clang 11/12 for example [1]), the following does not
result in a copy elision, and since `Error`'s copy dtor is elided,
results in a compile error:

```
  Expect<Something> foobar() {
    ...
    if (Error E = aCallReturningError())
      return E;
    ...
  }
```

Moving `E` would, conversely, result in the pessimizing-move warning on
more recent clangs ("moving a local object in a return statement
prevents copy elision")

We just need to make the `Expected` ctor taking an `Error` take it as a
r-value reference.

[1] https://lab.llvm.org/buildbot/#/builders/54/builds/10505

It's a common pattern that we have a machine type, but we don't care
which ARM64* platform we're dealing with. We already have
isAnyArm64 for that, but it does not fit cases where we use a switch
statement. With this helper, it's easy to simplify such cases by using
Triple::ArchType instead of machine type.

Note that llvm::support::endianness has been renamed to
llvm::endianness while becoming an enum class as opposed to an
enum. This patch replaces support::{big,little,native} with
llvm::endianness::{big,little,native}.

Similar to D125411, but for ARM64X.

ARM64X PE binaries are hybrids containing both ARM64EC and pure ARM64
variants in one file. They are usually linked by passing separate
ARM64EC and ARM64 object files to linker. Linked binaries use ARM64
machine and contain additional CHPE metadata in their load config.
CHPE metadata support is not part of this patch, I plan to send that later.

Using ARM64X as a machine type of object files themselves is somewhat
ambiguous, but such files are allowed by MSVC. It treats them as ARM64
or ARM64EC object, depending on the context. Such objects can be
produced with cvtres.exe -machine:arm64x.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D148517

Use deduction guides instead of helper functions.

The only non-automatic changes have been:

1. ArrayRef(some_uint8_pointer, 0) needs to be changed into ArrayRef(some_uint8_pointer, (size_t)0) to avoid an ambiguous call with ArrayRef((uint8_t*), (uint8_t*))
2. CVSymbol sym(makeArrayRef(symStorage)); needed to be rewritten as CVSymbol sym{ArrayRef(symStorage)}; otherwise the compiler is confused and thinks we have a (bad) function prototype. There was a few similar situation across the codebase.
3. ADL doesn't seem to work the same for deduction-guides and functions, so at some point the llvm namespace must be explicitly stated.
4. The "reference mode" of makeArrayRef(ArrayRef<T> &) that acts as no-op is not supported (a constructor cannot achieve that).

Per reviewers' comment, some useless makeArrayRef have been removed in the process.

This is a follow-up to https://reviews.llvm.org/D140896 that introduced
the deduction guides.

Differential Revision: https://reviews.llvm.org/D140955

This is the first patch of a patchset to add initial support for
ARM64EC. Basic documentation is available at
https://docs.microsoft.com/en-us/windows/uwp/porting/arm64ec-abi .
(Discourse post:
https://discourse.llvm.org/t/initial-patches-for-arm64ec-windows-11-now-posted/62449
.)

The file format for ARM64EC is basically identical to normal ARM64.
There are a few extra sections, but the existing code for reading ARM64
object files just works.

Differential Revision: https://reviews.llvm.org/D125411

Identified with readability-qualified-auto.

Most notably,

llvm/Object/Binary.h no longer includes llvm/Support/MemoryBuffer.h
llvm/Object/MachOUniversal*.h no longer include llvm/Object/Archive.h
llvm/Object/TapiUniversal.h no longer includes llvm/Object/TapiFile.h

llvm-project preprocessed size:
before: 1068185081
after:  1068324320

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D119457

This is a follow up to d1262a6e9, more explicit to cope with GCC smartness.

Differential Revision: https://reviews.llvm.org/D74666

The build failed with

  error: call to deleted constructor of 'llvm::Error'

errors.

This reverts commit 1c2241a7936bf85aa68aef94bd40c3ba77d8ddf2.