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

[via llvm-commits]

aengelke wrote:

> The bpf asm code is often read my humans and extra dot is a visual noise.

Is there any *technical* reason for this deviation? On all other ELF targets, local labels are prefixed with `.L`. Global private labels are already prefixed with `.L`. This would increase consistency with other ELF targets and tooling, in particular, basic block labels would no longer be added to the symbol table (as in literally all other targets).

Would removing the dot from private global symbols be an option, so that they are prefixed with `L` instead `.L`?

(Just for clarity: I don't care whether it's `L` or `.L`. I do, however, want to know why there's a deviation between local basic block labels and other local labels and to increase consistency if possible.)

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