[llvm] [llvm-mca][Darwin] Fix crash on .subsections_via_symbols in asm input (PR #182694)

[dan rouhana via llvm-commits]

dr7ana wrote:

@boomanaiden154 Thank you for the feedback. I will add tests. I promise this wasn't LLM generated, but I understand the concern with the recent deluge

https://github.com/llvm/llvm-project/pull/182694