Limited in what way? LLVM LTO works seamlessly if you use LLD on both macOS and Windows; that's what Chrome does, for example. LLVM LTO also works pretty seamle

Limited in what way? LLVM LTO works seamlessly if you use LLD on both macOS and Windows; that's what Chrome does, for example. LLVM LTO also works pretty seamlessly with ld64 on macOS; the linker needs libLTO, but the driver takes care of that for you.