[clang] [llvm] [dyndbg][Clang] Implement nested-ELF dynamic debugging support (PR #194860)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-5` while building `clang,llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/47812

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: DebugInfo/DynamicDebugging/attr-outer-tail-pad.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/clang -cc1 /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c -triple x86_64-unknown-unknown -debug-info-kind=constructor -fdynamic-debugging -o -     -emit-llvm --discard-dynamic-debugging-debug-module  | /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c --check-prefix=X86
# executed command: /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/clang -cc1 /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c -triple x86_64-unknown-unknown -debug-info-kind=constructor -fdynamic-debugging -o - -emit-llvm --discard-dynamic-debugging-debug-module
# .---command stderr------------
# | warning: ignoring -fdynamic-debugging: unable to create target: 'No available targets are compatible with triple "x86_64-unknown-unknown"' [-Wdynamic-debugging]
# | 1 warning generated.
# `-----------------------------
# executed command: /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/FileCheck /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c --check-prefix=X86
# .---command stderr------------
# | /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c:8:14: error: X86-SAME: expected string not found in input
# | // X86-SAME: "tail-pad-to-size"="5"
# |              ^
# | <stdin>:12:16: note: scanning from here
# | attributes #0 = { noinline nounwind optnone "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+cx8,+mmx,+sse,+sse2,+x87" }
# |                ^
# | <stdin>:12:111: note: possible intended match here
# | attributes #0 = { noinline nounwind optnone "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+cx8,+mmx,+sse,+sse2,+x87" }
# |                                                                                                               ^
# | 
# | Input file: <stdin>
# | Check file: /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |           1: ; ModuleID = '/Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c' 
# |           2: source_filename = "/Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/DebugInfo/DynamicDebugging/attr-outer-tail-pad.c" 
# |           3: target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128" 
# |           4: target triple = "x86_64-unknown-unknown" 
# |           5:  
# |           6: ; Function Attrs: noinline nounwind optnone 
# |           7: define dso_local i32 @f() #0 !dbg !4 { 
# | check:6      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |           8: entry: 
# |           9:  ret i32 0, !dbg !9 
# |          10: } 
# |          11:  
# |          12: attributes #0 = { noinline nounwind optnone "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-features"="+cx8,+mmx,+sse,+sse2,+x87" } 
# | check:7      ^~~~~~~~~~~~~~~
# | same:8'0                   {                                                                                                                                                                        search range start (exclusive)
# | same:8'1                                                                                                                                                                                            error: no match found in search range
# | same:8'2                                                                                                                   ?                                                                        possible intended match
# |          13:  
# |          14: !llvm.dbg.cu = !{!0} 
...

```

</details>

https://github.com/llvm/llvm-project/pull/194860