[libc] Add `strerror` and `strerror_k` to the GPU (#99083)

Summary:
The GPU ignores `errno` primarily, but targets want these functions to
be defined for certain C standard interfaces. This patch en

[libc] Add `strerror` and `strerror_k` to the GPU (#99083)

Summary:
The GPU ignores `errno` primarily, but targets want these functions to
be defined for certain C standard interfaces. This patch enables them
and makes the test function on non-Linux targets.

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[libc][errno] Remove previously added errno numbers (#92163)

Introduced in https://github.com/llvm/llvm-project/pull/91150. Not
needed anymore as https://github.com/llvm/llvm-project/pull/92041 fix

[libc][errno] Remove previously added errno numbers (#92163)

Introduced in https://github.com/llvm/llvm-project/pull/91150. Not
needed anymore as https://github.com/llvm/llvm-project/pull/92041 fixed
the root cause. `ENAMETOOLONG` and `EOVERFLOW` are well defined in
`<linux/errno.h>`.

Post mortem: Due to the previously missing inclusion of
`<linux/errno.h>` (fixed with
https://github.com/llvm/llvm-project/pull/92041), I misinterpreted an
undefined macro issue during the development of
https://github.com/llvm/llvm-project/pull/91150 as being caused by a
missing definition rather than by the missing inclusion of the linux
header. I realized too late that `ENAMETOOLONG` and `EOVERFLOW` were
correctly defined in `<linux/errno.h>` and that it was my missing
inclusion that caused the problem.

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[libc][errno] Remove non asm generic error number (#92172)

The following small thing caught my eye:

1) `EILSEQ` is not part of the generic asm error number macros. See the
[full list of generic

[libc][errno] Remove non asm generic error number (#92172)

The following small thing caught my eye:

1) `EILSEQ` is not part of the generic asm error number macros. See the
[full list of generic asm errno
codes](https://github.com/torvalds/linux/blob/4b95dc87362aa57bdd0dcbad109ca5e5ef3cbb6c/include/uapi/asm-generic/errno-base.h).
AFAIK the generic asm errno numbers are common between different
operating systems and architectures. `EILSEQ` is not part of this common
set of errno's.

2) `EILSEQ`'s value is wrong. During the addition of `EILSEQ` in
https://reviews.llvm.org/D151129, the value `35` was probably chosen as
its the consecutive number. This is not correct. The actual values can
be looked up for example here:
* [For Linux
kernel](https://github.com/search?q=repo%3Atorvalds%2Flinux+EILSEQ&type=code&p=1):
`EILSEQ = 84` (uapi; i.e. x86_64), `EILSEQ = 88` (mips), `EILSEQ = 47`
(parisc)
* [For Darwin
kernel](https://github.com/apple-oss-distributions/xnu/blob/main/bsd/sys/errno.h#L237):
`EILSEQ = 92`

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[libc][errno] Use macro instead of system header (#91150)

## Why
Currently, the system header `errno.h` is included in `libc_errno.h`,
which is supposed to be consumed by internal implementations

[libc][errno] Use macro instead of system header (#91150)

## Why
Currently, the system header `errno.h` is included in `libc_errno.h`,
which is supposed to be consumed by internal implementations only. As
unit and hermetic tests should never use `#include <errno.h>` but
instead use `#include "src/errno/libc_errno.h"`, we do not want to
implicitly include `errno.h`. In order to have a clear seperation
between those two, we want to pull out the definitions of errno numbers
from `errno.h`.

## What
* Extract the definitions of errno numbers from
[include/errno.h.def](https://github.com/llvm/llvm-project/pull/91150/files#diff-ed38ed463ed50571b498a5b69039cab58dc9d145da7f751a24da9d77f07781cd)
and place it under
[include/llvm-libc-macros/linux/error-number-macros.h](https://github.com/llvm/llvm-project/pull/91150/files#diff-d6192866629690ebb7cefa1f0a90b6675073e9642f3279df08a04dcdb05fd892)
* Provide mips-specific errno numbers in
[include/llvm-libc-macros/linux/mips/error-number-macros.h](https://github.com/llvm/llvm-project/pull/91150/files#diff-3fd35a4c94e0cc359933e497b10311d857857b2e173e8afebc421b04b7527743)
* Find definition of mips errno numbers in glibc
[here](https://github.com/bminor/glibc/blob/ea73eb5f581ef5931fd67005aa0c526ba43366c9/sysdeps/unix/sysv/linux/mips/bits/errno.h#L32-L50)
(equally defined in the Linux kernel)
* Provide sparc-specific errno numbers in
[include/llvm-libc-macros/linux/sparc/error-number-macros.h](https://github.com/llvm/llvm-project/pull/91150/files#diff-5f16ffb2a51a6f72ebd4403aca7e1edea48289c99dd5978a1c84385bec4f226b)
* Find definition of sparc errno numbers in glibc
[here](https://github.com/bminor/glibc/blob/ea73eb5f581ef5931fd67005aa0c526ba43366c9/sysdeps/unix/sysv/linux/sparc/bits/errno.h#L33-L51)
(equally defined in the Linux kernel)
* Include proxy header `errno_macros.h` instead of the system header
`errno.h` in `libc_errno.h`/`libc_errno.cpp`

Closes https://github.com/llvm/llvm-project/issues/80172

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[libc] fix clang-tidy llvm-header-guard warnings (#82679)


Towards the goal of getting `ninja libc-lint` back to green, fix the numerous
instances of:

warning: header guard does not follow pref

[libc] fix clang-tidy llvm-header-guard warnings (#82679)


Towards the goal of getting `ninja libc-lint` back to green, fix the numerous
instances of:

warning: header guard does not follow preferred style [llvm-header-guard]

This is because many of our header guards start with `__LLVM` rather than
`LLVM`.

To filter just these warnings:

$ ninja -k2000 libc-lint 2>&1 | grep llvm-header-guard

To automatically apply fixits:

$ find libc/src libc/include libc/test -name \*.h | \
xargs -n1 -I {} clang-tidy {} -p build/compile_commands.json \
-checks='-*,llvm-header-guard' --fix --quiet

Some manual cleanup is still necessary as headers that were missing header
guards outright will have them inserted before the license block (we prefer
them after).

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[libc] Make ErrnoSetterMatcher handle logging floating point values.

Along the way, couple of additional things have been done:

1. Move `ErrnoSetterMatcher.h` to `test/UnitTest` as all other matche

[libc] Make ErrnoSetterMatcher handle logging floating point values.

Along the way, couple of additional things have been done:

1. Move `ErrnoSetterMatcher.h` to `test/UnitTest` as all other matchers live
there now.
2. `ErrnoSetterMatcher` ignores matching `errno` on GPUs.

Reviewed By: jhuber6

Differential Revision: https://reviews.llvm.org/D151129

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[libc] Simplify generation of errno.h.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D140375