Tests for btree implementation used by range trees

Additional test cases for the btree implementation, see #9181.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: John Kennedy <john.kennedy@delphix.com>
Closes #9717

tests/zfs-tests/cmd/btree_test/Makefile.am

@@ -0,0 +1,32 @@
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright (c) 2019 by Delphix. All rights reserved.
+#
+
+include $(top_srcdir)/config/Rules.am
+
+pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/bin
+
+DEFAULT_INCLUDES += \
+	-I$(top_srcdir)/include \
+	-I$(top_srcdir)/lib/libspl/include
+
+# Unconditionally enable ASSERTs
+AM_CPPFLAGS += -DDEBUG -UNDEBUG
+
+pkgexec_PROGRAMS = btree_test
+btree_test_SOURCES = btree_test.c
+
+btree_test_LDADD = \
+	$(top_builddir)/lib/libavl/libavl.la \
+	$(top_builddir)/lib/libzpool/libzpool.la