block/raw-posix: fix compilation warning on OSX

block/raw-posix.c:947:19: warning: unused variable 's' [-Wunused-variable]
    BDRVRawState *s = aiocb->bs->opaque;

This variable is used only when on of the following macros are defined
CONFIG_XFS, CONFIG_FALLOCATE, CONFIG_FALLOCATE_PUNCH_HOLE or
CONFIG_FALLOCATE_ZERO_RANGE. Fortunately, CONFIG_FALLOCATE_PUNCH_HOLE
and CONFIG_FALLOCATE_ZERO_RANGE could be defined only along with
CONFIG_FALLOCATE. Therefore checking for CONFIG_XFS or CONFIG_FALLOCATE
would be enough.
Signed-off-by: NDenis V. Lunev <den@openvz.org>
CC: Peter Maydell <peter.maydell@linaro.org>
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/raw-posix.c

@@ -944,7 +944,9 @@ static ssize_t handle_aiocb_write_zeroes_block(RawPosixAIOData *aiocb)
 
 static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
 {
+#if defined(CONFIG_FALLOCATE) || defined(CONFIG_XFS)
     BDRVRawState *s = aiocb->bs->opaque;
+#endif
 
     if (aiocb->aio_type & QEMU_AIO_BLKDEV) {
         return handle_aiocb_write_zeroes_block(aiocb);