Add libzutil for libzfs or libzpool consumers

Adds a libzutil for utility functions that are common to libzfs and
libzpool consumers (most of what was in libzfs_import.c).  This
removes the need for utilities to link against both libzpool and
libzfs.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Don Brady <don.brady@delphix.com>
Closes #8050

lib/libzutil/Makefile.am

@@ -0,0 +1,27 @@
+include $(top_srcdir)/config/Rules.am
+
+# Suppress unused but set variable warnings often due to ASSERTs
+AM_CFLAGS += $(NO_UNUSED_BUT_SET_VARIABLE)
+
+DEFAULT_INCLUDES += \
+	-I$(top_srcdir)/include \
+	-I$(top_srcdir)/lib/libspl/include
+
+noinst_LTLIBRARIES = libzutil.la
+
+USER_C = \
+	zutil_device_path.c \
+	zutil_import.c \
+	zutil_nicenum.c \
+	zutil_pool.c
+
+nodist_libzutil_la_SOURCES = $(USER_C)
+
+libzutil_la_LIBADD = \
+	$(top_builddir)/lib/libavl/libavl.la \
+        $(top_builddir)/lib/libefi/libefi.la \
+	$(top_builddir)/lib/libtpool/libtpool.la
+
+libzutil_la_LIBADD += -lm $(LIBBLKID) $(LIBUDEV)
+
+EXTRA_DIST = $(USER_C)