[llvm] [BPF] Use ".L" local prefix label for basic blocks (PR #95103)

[via llvm-commits]

4ast wrote:

> 
> `llvm-objdump -d --symbolize-operands` is a way to improve readability of the disassembly, which doesn't need symbol table entries. With that feature, basic block labels are likely less relevant. In that case, we should favor more `.L` to match regular ELF targets.
> 
> There is a question whether `--symbolize-operands` should be the default for `llvm-objdump` BPF. While I don't favor that inconsistency, the discussion can be postponed to a difference place and not block the PR that switches to `.L`

well, this two PRs are related. Currently bpf users used to see L* labels in disasm and we have to preserve this behavior.
Turned out that they were in disasm by default because of bug/feature that L* labels were in symbol table.
Now if we remove them from symbol table either via this patch or via switching to ".L" we will regress disasm output, right?
I was hoping that switch to ".L" will make labels to appear in disasm automatically without extra flag.
If that is not the case we should treat both PRs as one and make sure disasm is still readable regardless of whether we pick L or .L

https://github.com/llvm/llvm-project/pull/95103