[libcxx-commits] [libcxx] Add C++23 stacktrace (P0881R7) (PR #136528)

[Steve O'Brien via libcxx-commits]

elsteveogrande wrote:

More diagnostics re: that apple-system issue.

Running test program locally, same error as in CI:
```
~/code/llvm-project$ build/apple-system/cxx/libcxx/test/libcxx/stacktrace/Output/simple.o3.nosplit.pass.cpp.dir/t.tmp.exe
dyld[40817]: Symbol not found: __ZNSt3__112__stacktrace4base12current_implEmm
  Referenced from: <15D1B55C-FB38-3D06-A73B-2269ED9FD3D8> /Users/steve/code/llvm-project/build/apple-system/cxx/libcxx/test/libcxx/stacktrace/Output/simple.o3.nosplit.pass.cpp.dir/t.tmp.exe (built for macOS 15.6.1 which is newer than running OS)
  Expected in:     <643ED232-CE19-3F63-8015-0AEE768C002F> /usr/lib/libc++.1.dylib
Abort trap: 6
```

Test prog file's UUID definitely matches.  (Not sure why it wouldn't, just confirming)
```
~/code/llvm-project$ llvm-dwarfdump -a build/apple-system/cxx/libcxx/test/libcxx/stacktrace/Output/simple.o3.nosplit.pass.cpp.dir/t.tmp.exe
build/apple-system/cxx/libcxx/test/libcxx/stacktrace/Output/simple.o3.nosplit.pass.cpp.dir/t.tmp.exe:	file format Mach-O arm64
UUID: 15D1B55C-FB38-3D06-A73B-2269ED9FD3D8 (arm64) build/apple-system/cxx/libcxx/test/libcxx/stacktrace/Output/simple.o3.nosplit.pass.cpp.dir/t.tmp.exe
```

Indeed there's no `/usr/lib/libc++.1.dylib` on my system.

The dylib I built:
```
~/code/llvm-project$ llvm-dwarfdump -a build/apple-system/cxx/lib/libc++.dylib
build/apple-system/cxx/lib/libc++.dylib:	file format Mach-O arm64
UUID: 4E121B42-C36B-3939-8D9B-7C05053C9425 (arm64) build/apple-system/cxx/lib/libc++.dylib
```

https://github.com/llvm/llvm-project/pull/136528