Avoid build failure when sdbus++ tool is disabled

Few examples provided as a part of the repository are dependent on the
sdbus++ code generation tool, and the compilation will fail trying to
build the examples even in cases where the user disables sdbusapp during
configuration using --disable-sdbuspp option.

- Made a change in example/Makefile.am to build the examples which are
  dependent on sdbus++ tool(which is dependent on few python packages)
  only when the sdbuspp is enabled during configuration.

Resolves openbmc/sdbusplus#19

Change-Id: I1453536fd4c7df35e66f2ccfe7a890cced0d155d
Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
diff --git a/example/Makefile.am b/example/Makefile.am
index c62fcf9..6d43c4a 100644
--- a/example/Makefile.am
+++ b/example/Makefile.am
@@ -1,4 +1,8 @@
-noinst_PROGRAMS = calculator-server list-users
+noinst_PROGRAMS = list-users
+
+list_users_SOURCES = list-users.cpp
+list_users_CXXFLAGS = $(SYSTEMD_CFLAGS) -I$(top_srcdir)
+list_users_LDADD = $(SYSTEMD_LIBS) ../libsdbusplus.la
 
 if BOOST
 noinst_PROGRAMS += asio-example
@@ -23,6 +27,8 @@
     $(BOOST_LDFLAGS)
 endif
 
+if WANT_SDBUSPP
+noinst_PROGRAMS += calculator-server
 calculator_server_generated_files = \
 	net/poettering/Calculator/server.hpp \
 	net/poettering/Calculator/server.cpp \
@@ -37,10 +43,6 @@
 calculator_server_CXXFLAGS = $(SYSTEMD_CFLAGS) -I$(top_srcdir)
 calculator_server_LDADD = $(SYSTEMD_LIBS) ../libsdbusplus.la
 
-list_users_SOURCES = list-users.cpp
-list_users_CXXFLAGS = $(SYSTEMD_CFLAGS) -I$(top_srcdir)
-list_users_LDADD = $(SYSTEMD_LIBS) ../libsdbusplus.la
-
 BUILT_SOURCES = \
 	$(calculator_server_generated_files) \
 	$(calculator_markdown_generated_files)
@@ -80,3 +82,4 @@
 	@top_srcdir@/tools/sdbus++ \
 	    -r $(srcdir) -t $(top_builddir)/tools/sdbusplus/templates \
 	    error markdown net.poettering.Calculator >> $@
+endif