Enable configure of just sdbus++

Change-Id: I9910ef3c8d632ea4ed71dbf49c48c0cd798441f7
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/Makefile.am b/Makefile.am
index 5b39bc1..c60ff10 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,3 +1,5 @@
+if WANT_LIBSDBUSPLUS
+
 nobase_include_HEADERS = \
 	mapbox/recursive_wrapper.hpp \
 	mapbox/variant.hpp \
@@ -16,4 +18,5 @@
 	sdbusplus/utility/type_traits.hpp \
 	sdbusplus/vtable.hpp
 
+endif
 SUBDIRS = test tools