fcntl: Fix build failure for some architectures with Linux 5.19
Starting from Linux 5.19, the kernel UAPI headers now only define __ARCH_FLOCK64_PAD if the architecture actually needs padding in struct flock64. Wrap its use with #ifdef,
Backport patch from, https://git.kernel.org/pub/scm/libs/klibc/klibc.git/commit/?id=bb2fde5ddbc18a2e7795ca4d24759230c2aae9d0