Add wrapper stub for zfs_cmd ioctl to libzpool

FreeBSD needs a wrapper for handling zfs_cmd ioctls.
In libzfs this is handled by zfs_ioctl. However, here
we need to wrap the call directly.

Reviewed-by: Allan Jude <allanjude@freebsd.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #9511

lib/libzutil/Makefile.am

@@ -17,7 +17,8 @@ USER_C = \
 if BUILD_LINUX
 USER_C += \
 	os/linux/zutil_device_path_os.c \
-	os/linux/zutil_import_os.c
+	os/linux/zutil_import_os.c \
+	os/linux/zutil_compat.c
 endif
 
 nodist_libzutil_la_SOURCES = $(USER_C)

lib/libzutil/os/linux/zutil_compat.c

@@ -0,0 +1,30 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/zfs_ioctl.h>
+#include <libzutil.h>
+
+int
+zfs_ioctl_fd(int fd, unsigned long request, zfs_cmd_t *zc)
+{
+	return (ioctl(fd, request, zc));
+}