SmallPtrSet.h and TimeProfiler.h are unused. CommandLine.h is only
needed for the UseNewDbgInfoFormat declare, which can be moved to the
places that need it.

So long as ld -r links using bitcode always result in an ELF object, and
not a merged bitcode object, the output form a relocatable link using
FatLTO objects should not have a .llvm.lto section. Prior to this, using
the object code sections would cause the bitcode section in the output
of a relocatable link to be corrupted, by concatenating all the
.llvm.lto
sections together.

This patch discards SHT_LLVM_LTO sections when not using
--fat-lto-objects, so that the relocatable ELF output won't contain
inalid bitcode.

GNU ld's relocatable linking behaviors:

* Sections with the `SHF_GROUP` flag are handled like sections matched
  by the `--unique=pattern` option. They are processed like orphan
  sections and ignored by input section descriptions.
* Section groups' (usually named `.group`) content is updated as the
  section indexes are updated. Section groups can be discarded with
  `/DISCARD/ : { *(.group) }`.

`-r --force-group-allocation` discards section groups and allows
sections with the `SHF_GROUP` flag to be matched like normal sections.
If two section group members are placed into the same output section,
their relocation sections (if present) are combined as well.
This behavior can be useful when -r output is used as a pseudo shared
object (e.g., FreeBSD's amd64 kernel modules, CHERIoT compartments).

This patch implements --force-group-allocation:

* Input SHT_GROUP sections are discarded.
* Input sections do not get the SHF_GROUP flag, so `addInputSec`
  will combine relocation sections if their relocated section group
  members are combined.

The default behavior is:

* Input SHT_GROUP sections are retained.
* Input SHF_GROUP sections can be matched (unlike GNU ld)
* Input SHF_GROUP sections keep the SHF_GROUP flag, so `addInputSec`
  will create different OutputDesc copies.

GNU ld provides the `FORCE_GROUP_ALLOCATION` command, which is not
implemented.

Pull Request: https://github.com/llvm/llvm-project/pull/94704

This reverts commit 7832769d329ead264aff238c06dce086b3a74922.

This was reverted prior due to a test failure on the windows builder. I
think this was because we didn't specify the triple and assumed windows.
The other tests use the full triple specifying linux, so we follow suite
here.

---

We are using PLTs for cortex-m33 which only supports thumb. More
specifically, this is for a very restricted use case. There's no MMU so
there's no sharing of virtual addresses between two processes, but this
is fine. The MCU is used for running [chre
nanoapps](https://android.googlesource.com/platform/system/chre/+/HEAD/doc/nanoapp_overview.md)
for android. Each nanoapp is a shared library (but effectively acts as
an executable containing a test suite) that is loaded and run on the MCU
one binary at a time and there's only one process running at a time, so
we ensure that the same text segment cannot be shared by two different
running executables. GNU LD supports thumb PLTs but we want to migrate
to a clang toolchain and use LLD, so thumb PLTs are needed.

Reverts llvm/llvm-project#86223

windows pre-merge is broken.

We are using PLTs for cortex-m33 which only supports thumb. More
specifically, this is for a very restricted use case. There's no MMU so
there's no sharing of virtual addresses between two processes, but this
is fine. The MCU is used for running [chre
nanoapps](https://android.googlesource.com/platform/system/chre/+/HEAD/doc/nanoapp_overview.md)
for android. Each nanoapp is a shared library (but effectively acts as
an executable containing a test suite) that is loaded and run on the MCU
one binary at a time and there's only one process running at a time, so
we ensure that the same text segment cannot be shared by two different
running executables. GNU LD supports thumb PLTs but we want to migrate
to a clang toolchain and use LLD, so thumb PLTs are needed.

This patch adds lld support for:

- Dynamic R_AARCH64_AUTH_* relocations (without including RELR compressed AUTH
relocations) as described here:
https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#auth-variant-dynamic-relocations

- .note.AARCH64-PAUTH-ABI-tag section as defined here
https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#elf-marking

Depends on #72713 and #85231

---------

Co-authored-by: Peter Collingbourne <peter@pcc.me.uk>
Co-authored-by: Fangrui Song <i@maskray.me>

For a DSO with all DT_NEEDED entries accounted for, if it contains an
undefined non-weak symbol that shares a name with a non-exported
definition (hidden visibility or localized by a version script), and
there is no DSO definition, we should report an error.

#70769 implemented the error when we see `ref.so def-hidden.so`. This patch
implementes the error when we see `def-hidden.so ref.so`, matching GNU
ld.

Close #86777

`TargetEndianness` is long and unwieldy. "Target" in the name is confusing. Rename it to "Endianness".

I cannot find noticeable out-of-tree users of `TargetEndianness`, but
keep `TargetEndianness` to make this patch safer. `TargetEndianness`
will be removed by a subsequent change.