[Bug tree-optimization/114952] False positive -Wmaybe-uninitialized starting at -O3 in libbpf

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114952

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Most likely GCC does not know errno is non-zero after the call to elf_open and
checking `fd < 0`.
Adding:
  if (ret == 0) __builtin_unreachable();
After the assignment of `ret = -errono;` fixes the warning.