This change is related merging some of the APIs in HostInfoLinux into
HostInfoPosix.

Here is the reference PR comment:

https://github.com/llvm/llvm-project/pull/117906#discussion_r1865427495,
https://github.com/llvm/llvm-project/pull/117906#discussion_r1861616945

No behavior change.

The qHostInfo packet in the gdb-remote communication protocol specifies
that distribution_id can be set, so lldb handles that. But we store that
in the ArchSpec representing the "Host" platform (whatever platform the
debug server is running on). This field is otherwise unused in ArchSpec,
so it would be a lot easier if we stored that information at the
gdb-remote communication layer.

Sidenote: The distribution_id field is currently unused but I did not
want to remove it in case some folks found it useful (e.g. in downstream
forks).

Differential Revision: https://reviews.llvm.org/D149697

This patch replaces (llvm::|)Optional< with std::optional<.  I'll post
a separate patch to clean up the "using" declarations, #include
"llvm/ADT/Optional.h", etc.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

This patch adds #include <optional> to those files containing
llvm::Optional<...> or Optional<...>.

I'll post a separate patch to actually replace llvm::Optional with
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated.  The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

Use this instead of `*_LIBDIR_SUFFIX`, from which it is computed.

This gets us ready for D130586, in which `*_LIBDIR_SUFFIX` is
deprecated.

Differential Revision: https://reviews.llvm.org/D132300

This reverts commit f7a33090a91015836497c75f173775392ab0304d.

Unfortunately this causes a number of failures that didn't show up in my
local build.

We held off on this before as `LLVM_LIBDIR_SUFFIX` conflicted with it.
Now we return this.

`LLVM_LIBDIR_SUFFIX` is kept as a deprecated way to set
`CMAKE_INSTALL_LIBDIR`. The other `*_LIBDIR_SUFFIX` are just removed
entirely.

I imagine this is too potentially-breaking to make LLVM 15. That's fine.
I have a more minimal version of this in the disto (NixOS) patches for
LLVM 15 (like previous versions). This more expansive version I will
test harder after the release is cut.

Reviewed By: sebastian-ne, ldionne, #libc, #libc_abi

Differential Revision: https://reviews.llvm.org/D130586