[llvm] AArch64: Fix hardcoding calling convention of sincos_stret (PR #144336)

[Benjamin Maxwell via llvm-commits]

https://github.com/MacDue commented:

This seems fine... Did this cause any specific issue? 

I can see the CC was set for the "WatchABI", which I guess was ignored: https://github.com/llvm/llvm-project/blob/01f9dff61fb028f69493a44616014256dee5fb2a/llvm/lib/IR/RuntimeLibcalls.cpp#L382-L391

https://github.com/llvm/llvm-project/pull/144336