compiler: Switch to DWARF 5 by default for zig cc and the LLVM backend.

[alexrp]

This is the same version we're targeting for the self-hosted backends.

[alexrp]

@Rexicon226 are you interested in this? https://github.com/ziglang/zig/actions/runs/12336006799/job/34428085051?pr=22235

error: fatal linker error: unhandled relocation type R_RISCV_SET_ULEB128 at offset 0x163ec
    note: in C:\Users\CI\actions-runner-3\_work\zig\zig\build-release\zig-global-cache\o\34901702e1b80b35a620f8084e08f477\libcompiler_rt.a(C:\Users\CI\actions-runner-3\_work\zig\zig\build-release\zig-global-cache\o\34901702e1b80b35a620f8084e08f477\libcompiler_rt.a.o/):.debug_loclists

[Rexicon226]

Sure, let me quickly implement that and give you a commit.

[Rexicon226]

here you go! Rexicon226@cba1b3b

i'm still not 100% sure what these relocations are actually doing with dwarf but I objdumped some binaries and they have the right source code locations 🤷

[alexrp]

Nice, thanks!

[alexrp]

Hmm, the self-hosted WebAssembly linker is not having a good time with this: https://github.com/ziglang/zig/actions/runs/12337349953/job/34430969217?pr=22235

error: unknown section: .debug_str_offsets

I guess I'll mark this as draft until #22220 is merged; no point mucking about in the linker code until then.