Repro for clang GMLT + LTO missing C++ namespace info

gistfile1.txt

% clang++ --version
Apple clang version 15.0.0 (clang-1500.0.40.1)
Target: arm64-apple-darwin23.2.0
Thread model: posix
InstalledDir: /Applications/Xcode_15.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

% cat test.cc
#include <stdio.h>

namespace foo {

__attribute__((noinline))
void f() {
  printf("yay\n");
}

__attribute__((always_inline)) void g() {
  f();
}

void h() {
  g();
};

}  // namespace foo

int main(int argc, char** argv) {
  foo::h();
}

% clang++ -gmlt -Os -flto -std=c++17 -c -o test.o test.cc
% clang++ -gmlt -Os -flto -Wl,-object_path_lto,lto.o -o test test.o
% dsymutil test

% dwarfdump test.dSYM/Contents/Resources/DWARF/test
test.dSYM/Contents/Resources/DWARF/test:	file format Mach-O arm64

.debug_info contents:
0x00000000: Compile Unit: length = 0x00000094, format = DWARF32, version = 0x0004, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x00000098)

0x0000000b: DW_TAG_compile_unit
              DW_AT_producer	("Apple clang version 15.0.0 (clang-1500.0.40.1)")
              DW_AT_language	(DW_LANG_C_plus_plus_14)
              DW_AT_name	("test.cc")
              DW_AT_LLVM_sysroot	("/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk")
              DW_AT_APPLE_sdk	("MacOSX.sdk")
              DW_AT_stmt_list	(0x00000000)
              DW_AT_comp_dir	("/Users/benhamilton")
              DW_AT_APPLE_optimized	(true)
              DW_AT_low_pc	(0x0000000100003f6c)
              DW_AT_high_pc	(0x0000000100003f90)

0x00000032:   DW_TAG_subprogram
                DW_AT_low_pc	(0x0000000100003f6c)
                DW_AT_high_pc	(0x0000000100003f78)
                DW_AT_APPLE_omit_frame_ptr	(true)
                DW_AT_call_all_calls	(true)
                DW_AT_name	("f")

0x00000043:   DW_TAG_subprogram
                DW_AT_name	("g")
                DW_AT_inline	(DW_INL_inlined)

0x00000049:   DW_TAG_subprogram
                DW_AT_name	("h")
                DW_AT_inline	(DW_INL_inlined)

0x0000004f:   DW_TAG_subprogram
                DW_AT_low_pc	(0x0000000100003f78)
                DW_AT_high_pc	(0x0000000100003f90)
                DW_AT_call_all_calls	(true)
                DW_AT_name	("main")

0x00000060:     DW_TAG_inlined_subroutine
                  DW_AT_abstract_origin	(0x0000000000000049 "h")
                  DW_AT_low_pc	(0x0000000100003f80)
                  DW_AT_high_pc	(0x0000000100003f84)
                  DW_AT_call_file	("/Users/benhamilton/test.cc")
                  DW_AT_call_line	(21)
                  DW_AT_call_column	(0x03)

0x00000074:       DW_TAG_inlined_subroutine
                    DW_AT_abstract_origin	(0x0000000000000043 "g")
                    DW_AT_low_pc	(0x0000000100003f80)
                    DW_AT_high_pc	(0x0000000100003f84)
                    DW_AT_call_file	("/Users/benhamilton/test.cc")
                    DW_AT_call_line	(15)
                    DW_AT_call_column	(0x03)

0x00000088:       NULL

0x00000089:     DW_TAG_call_site
                  DW_AT_call_origin	(0x00000032)
                  DW_AT_call_return_pc	(0x0000000100003f84)

0x00000096:     NULL

0x00000097:   NULL

% nm test.dSYM/Contents/Resources/DWARF/test | c++filt
0000000100003f6c t foo::f()
0000000100000000 T __mh_execute_header
0000000100003f78 T _main