Generate client headers for all interfaces

Use sdbus++'s client-header option to generate client header files for
the interfaces.

For now the header includes the interface's string, so that a user
will not have to define their own interface string anymore.

Tested: Verify the client.hpp are generated for each interface and get
        installed.

Depends-On: Idafc4724efa88a2dfd37e3f7735732c45171fd88
Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I966608e08b1745468fa37b30f6135e16e184a6bf
diff --git a/Makefile.am b/Makefile.am
index 933e339..72ac4dc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -8,8 +8,8 @@
 libphosphor_dbus_la_LDFLAGS = $(SYSTEMD_LIBS) $(SDBUSPLUS_LIBS) -version-info 0:0:0 -shared
 libphosphor_dbus_la_CXXFLAGS = $(SYSTEMD_CFLAGS) $(SDBUSPLUS_CFLAGS) -flto
 
-BUILT_SOURCES = libphosphor_dbus.cpp
-CLEANFILES = libphosphor_dbus.cpp
+BUILT_SOURCES = libphosphor_dbus.cpp libphosphor_dbus_client.hpp
+CLEANFILES = libphosphor_dbus.cpp libphosphor_dbus_client.hpp
 
 pkgconfiglibdir = ${libdir}/pkgconfig
 pkgconfiglib_DATA = phosphor-dbus-interfaces.pc