[LLD][ELF] Incorrect source location in undefined symbol error

[mysterymath]

We've hit a situation where an undefined symbol error in LLD shows an incorrect source location:

ld.lld: error: undefined hidden symbol: std::__ktl::__hash_memory(void const*, unsigned long)
>>> referenced by span:561 (../../prebuilt/third_party/clang/linux-x64/bin/../include/c++/v1/span:561)
>>>               libboot-shim.devicetree-riscv-cpu-topology-item.cc.o:(boot_shim::RiscvDevicetreeCpuTopologyItemBase::OnDone()) in archive usr/local/google/home/mcgrathr/tq/fuchsia/out/bringup.riscv64-clang/kernel.phys_riscv64/obj/zircon/kernel/phys/lib/boot-shim/libboot-shim.a
>>> referenced by alloc_checker.h:66 (../../zircon/system/ulib/fbl/include/fbl/alloc_checker.h:66)
>>>               libboot-shim.devicetree-riscv-cpu-topology-item.cc.o:(boot_shim::RiscvDevicetreeCpuTopologyItemBase::OnDone()) in archive usr/local/google/home/mcgrathr/tq/fuchsia/out/bringup.riscv64-clang/kernel.phys_riscv64/obj/zircon/kernel/phys/lib/boot-shim/libboot-shim.a

A disassembly with llvm-objdump --demangle -dlr shows the correct location:

; ./../../prebuilt/third_party/clang/linux-x64/bin/../include/c++/v1/__string/char_traits.h:537
     390: 8566         	mv	a0, s9
     392: 85d2         	mv	a1, s4
     394: 00000097     	auipc	ra, 0x0
		0000000000000394:  R_RISCV_CALL_PLT	std::__ktl::__hash_memory(void const*, unsigned long)
		0000000000000394:  R_RISCV_RELAX	*ABS*
     398: 000080e7     	jalr	ra <.Lpcrel_hi2+0x21e>

I noticed that the code in LLD wasn't using the usual getLineInfoForAddress in DWARFContext, but changing it to do so didn't make any difference. It looks like llvm-objdump is using the LLVM symbolizer library instead of directly using the DWARF library; maybe there's some smarts there that are making the difference? I haven't yet tried getting LLD to use the symbolizer library.

Originally found in Fuchsia. See here for the LLD reproducer: https://issues.fuchsia.dev/407569434