[llvm] [SROA] Propagate no-signed-zeros(nsz) fast-math flag on the phi node using function attribute (PR #83381)

[Nuno Lopes via llvm-commits]

nunoplopes wrote:

> @nunoplopes As far as I can tell, alive2 does not have support for the `no-signed-zeros-fp-math` attribute, so I think that's expected.

Ah, thanks, I missed that.
To my defense, it's not documented in LangRef 😅

https://github.com/llvm/llvm-project/pull/83381