[llvm] [DWARF] Emit a worst-case prologue_end flag for pathological inputs (PR #107849)

[Pavel Labath via llvm-commits]

labath wrote:

It's the latter (the test checks lldb's output when it stops on line zero), and it just so happens that I have a patch (#115876) up which modifies that test. I wasn't able to get it to do what I wanted using the approach in that test, so I implemented something hopefully more robust (it explicitly finds an instruction with line==0 and sets a breakpoint there). I think that should be compatible your changes here.

https://github.com/llvm/llvm-project/pull/107849