[llvm] MC: Better handle backslash-escaped symbols (PR #158780)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Could you please also add an LLVM IR test along the lines of https://llvm.godbolt.org/z/Ea7WzdczE, so we can see the escaping is now correct?

https://github.com/llvm/llvm-project/pull/158780