[llvm] [X86][CodeGen] Restrict F128 lowering to GNU environment (PR #81664)

[Nikita Popov via llvm-commits]

nikic wrote:

This change only makes sense if X64 Android actually uses f128 arithmetic rather than f80 arithmetic in the `*l` builtins -- does it?

https://github.com/llvm/llvm-project/pull/81664