[llvm] [RFC][LLVM] Emit dwarf data for changed-signature and new functions (PR #165310)

[via llvm-commits]

yonghong-song wrote:

Just uploaded a new version which
  - disable emission of true signature by default. Adding option `-mllvm -enable-changed-func-dbinfo` to enable true signature generation.
  - Add more functions to true signature category including (1) functions having > 8 byte parameter, (2). any non-source function e.g. foo.llvm.<hash> even if foo has the same signature with foo.llvm.<hash>. and (3) any signature-changed functions. These changes make more function tracable by bpf programs esp. with fentry/fexit bpf programs.

https://github.com/llvm/llvm-project/pull/165310