llvm > 19 segfaults on LLVM ADCE post autodiff using pybamm dfn model

[martinjrobins]

• segfault in LLVM ADCE: AggressiveDeadCodeElimination::markLive (post autodiff optimisation pass)
• does not occur if calc_out_rgrad or calc_stop_rgrad is not compiled, so something to do with both of them being in the module at once?

[martinjrobins]

I played around with creating similar models, but could not reproduce the segfault on simpler models