OpenZFS restructuring - zpool

Factor Linux specific functions out of the zpool command.
    
Reviewed-by: Allan Jude <allanjude@freebsd.org>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #9333

cmd/zpool/Makefile.am

@@ -2,7 +2,8 @@ include $(top_srcdir)/config/Rules.am
 
 DEFAULT_INCLUDES += \
 	-I$(top_srcdir)/include \
-	-I$(top_srcdir)/lib/libspl/include
+	-I$(top_srcdir)/lib/libspl/include \
+	-I.
 
 sbin_PROGRAMS = zpool
 
@@ -13,6 +14,10 @@ zpool_SOURCES = \
 	zpool_util.h \
 	zpool_vdev.c
 
+if BUILD_LINUX
+zpool_SOURCES += os/linux/zpool_vdev_os.c
+endif
+
 zpool_LDADD = \
 	$(top_builddir)/lib/libnvpair/libnvpair.la \
 	$(top_builddir)/lib/libuutil/libuutil.la \