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

[Jeremy Morse via llvm-commits]

jmorse wrote:

CI-checking believes there's something wrong on Linux-only; check-all on my Linux machine doesn't find anything wrong, and CI isn't indicating what test might be failing. Thus: I shall submit and see what happens >_>

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