tools/virtio: fix up oot build

oot build tends to help uncover bugs so it's worth keeping around,
as long as it's low effort.
add stubs for a couple of macros virtio gained recently,
and disable vdpa in the test build.

Message-ID: <[e-mail]>
Acked-by: Jason Wang <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

tools/virtio/Makefile

···
 	CONFIG_VHOST_NET=n \
 	CONFIG_VHOST_SCSI=n \
 	CONFIG_VHOST_VSOCK=n \
-	CONFIG_VHOST_RING=n
-OOT_BUILD=KCFLAGS="-I "${OOT_VHOST} ${MAKE} -C ${OOT_KSRC} V=${V}
+	CONFIG_VHOST_RING=n \
+	CONFIG_VHOST_VDPA=n
+OOT_BUILD=KCFLAGS="-include "`pwd`"/oot-stubs.h -I "${OOT_VHOST} ${MAKE} -C ${OOT_KSRC} V=${V}
 oot-build:
 	echo "UNSUPPORTED! Don't use the resulting modules in production!"
 	${OOT_BUILD} M=`pwd`/vhost_test

tools/virtio/oot-stubs.h

···
+#include <linux/bug.h>
+#include <linux/string.h>
+#include <linux/virtio_features.h>
+
+#ifndef VIRTIO_FEATURES_BITS
+#define VIRTIO_FEATURES_BITS 128
+#endif
+#ifndef VIRTIO_U64
+#define VIRTIO_U64(b)           ((b) >> 6)
+#endif