My build of LLDB is all the time loading targets with a version of
libc++ that was built with gcc that uses the DW_FORM 0x1e that is not
implemented by LLVM, and I doubt it'll ever implement it. It's used for
some 128 bit encoding of numbers, which is just very weird.
Because of this, LLDB is showing some warnings all the time for my
users, so I'm adding a flag to control the enablement of this warning.

@walter-erquinigo found the the [PR with testing and a fix for
DebugInfoD](https://github.com/llvm/llvm-project/pull/98344) caused an
issue when working with stripped binaries.

The issue is that when you're working with split-dwarf, there are *3*
possible files: The stripped binary the user is debugging, the
"only-keep-debug" *or* unstripped binary, plus the `.dwp` file. The
debuginfod plugin should provide the unstripped/OKD binary. However, if
the debuginfod plugin fails, the default symbol locator plugin will just
return the stripped binary, which doesn't help. So, to address that, the
SymbolVendorELF code checks to see if the SymbolLocator's
ExecutableObjectFile request returned the same file, and bails if that's
the case. You can see the specific diff as the second commit in the PR.

I'm investigating adding a test: I can't quite get a simple repro, and
I'm unwilling to make any additional changes to Makefile.rules to this
diff, for Pavlovian reasons.

This is a reapply of https://github.com/llvm/llvm-project/pull/92328 and
https://github.com/llvm/llvm-project/pull/93839.

It now passes the
[test](https://github.com/llvm/llvm-project/commit/de3f1b6d68ab8a0e827db84b328803857a4f60df),
which crashes with the original reverted changes.

This reverts commit 2fa1220a37a3f55b76a29803d8333b3a3937d53a.
This reverts commit b9496a74eb4029629ca2e440c5441614e766f773.

The patch #98344 causes a crash in LLDB when parsing some files like `numpy.libs/libgfortran-daac5196.so.5.0.0` on graviton (you can download it in https://drive.google.com/file/d/12ygLjJwWpzdYsrzBPp1JGiFHxcgM0-XY/view?usp=drive_link if you want to troubleshoot yourself).

The assert that is hit is the following:

```
llvm-project/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp:2452: std::pair<unsigned int, std::map<long unsigned int, lldb_private::AddressClass> > ObjectFileELF::ParseSymbolTable(lldb_private::Symtab*, lldb::user_id_t, lldb_private::Section*): Assertion `strtab->GetObjectFile() == this' failed.
[383588:383636:20240716,025305.572639:ERROR crashpad_client_linux.cc:780] Crashpad isn't enabled
```

This object file doesn't have apparently a strings table but LLDB still tries to process it due to the code that is being reverted.

This is all the tests and fixes I've had percolating since my first
attempt at this in January. After 6 months of trying, I've given up on
adding the ability to test DWP files in LLDB API tests. I've left both
the tests (disabled) and the changes to Makefile.rules in place, in the
hopes that someone who can configure the build bots will be able to
enable the tests once a non-borked dwp tool is widely available.

Other than disabling the DWP tests, this continues to be the same diff
that I've tried to land and
[not](https://github.com/llvm/llvm-project/pull/90622)
[revert](https://github.com/llvm/llvm-project/pull/87676)
[five](https://github.com/llvm/llvm-project/pull/86812)
[times](https://github.com/llvm/llvm-project/pull/85693)
[before](https://github.com/llvm/llvm-project/pull/96802). There are a
couple of fixes that the testing exposed, and I've abandoned the DWP
tests because I want to get those fixes finally upstreamed, as without
them DebugInfoD is less useful.

Reverts llvm/llvm-project#96802

Attempt #5 fails. It's been 6 months. I despise Makefile.rules and have
no ability to even *detect* these failures without _landing_ a diff. In
the mean time, we have no testing for DWP files at all (and a regression
that was introduced, that I fix with this diff) so I'm going to just
remove some of the tests and try to land it again, but with less testing
I guess.

This is the same diff I've put up at many times before. I've been trying
to add some brand new functionality to the LLDB test infrastucture
(create split-dwarf files!), and we all know that no good deed goes
unpunished. The last attempt was reverted because it didn't work on the
Fuchsia build.

There are no code differences between this and
[the](https://github.com/llvm/llvm-project/pull/90622)
[previous](https://github.com/llvm/llvm-project/pull/87676)
[four](https://github.com/llvm/llvm-project/pull/86812)
[diffs](https://github.com/llvm/llvm-project/pull/85693) landed &
reverted (due to testing infra failures). The only change in this one is
the way `dwp` is being identified in `Makefile.rules`.

Thanks to @petrhosek for helping me figure out how the fuchsia builders
are configured. I now prefer to use llvm-dwp and fall back to gnu's dwp
if the former isn't found. Hopefully this will work everywhere it needs
to.

If ParseStructureLikeDIE (or ParseEnum) encountered a declaration DIE,
it would call FindDefinitionTypeForDIE. This returned a fully formed
type, which it achieved by recursing back into ParseStructureLikeDIE
with the definition DIE.

This obscured the control flow and caused us to repeat some work (e.g.
the UniqueDWARFASTTypeMap lookup), but it mostly worked until we tried
to delay the definition search in #90663. After this patch, the two
ParseStructureLikeDIE calls were no longer recursive, but rather the
second call happened as a part of the CompleteType() call. This opened
the door to inconsistencies, as the second ParseStructureLikeDIE call
was not aware it was called to process a definition die for an existing
type.

To make that possible, this patch removes the recusive type resolution
from this function, and leaves just the "find definition die"
functionality. After finding the definition DIE, we just go back to the
original ParseStructureLikeDIE call, and have it finish the parsing
process with the new DIE.

While this patch is motivated by the work on delaying the definition
searching, I believe it is also useful on its own.

This patch adds support for the new foreign type unit support in
.debug_names. Features include:
- don't manually index foreign TUs if we have info for them
- only use the type unit entries that match the .dwo files when we have
a .dwp file
- fix type unit lookups for .dwo files
- fix crashers that happen due to PeekDIEName() using wrong offsets where an entry had DW_IDX_comp_unit and DW_IDX_type_unit entries and when we had no type unit support, it would cause us to think it was a normal DIE in .debug_info from the main executable.

---------

Co-authored-by: paperchalice <liujunchang97@outlook.com>