It's possible to have an `ld-path` point to a linker that doesn't have the `ld.lld` filename (e.g. linker wrapper that may emit telemetry before invoking the linker). This was causing mis-compilations with fatLTO since the check couldn't reliably detect that it was using lld. Instead, rely on the value from `-fuse-ld` to determine whether lld is enabled.