Make sure rpath gets added for ostree libs

We bundle ostree in the package, so we need to make sure an rpath
gets set pointing to our bundled library.

The Makefiles are missing the OSTREE_LIBS (and so the -Wl,-rpath),
so add them in.
--- flatpak-1.0.1/session-helper/Makefile.am.inc.old	2018-08-08 16:56:20.000000000 +0200
+++ flatpak-1.0.1/session-helper/Makefile.am.inc	2018-09-12 13:23:08.304959872 +0200
@@ -12,5 +12,5 @@
 	session-helper/flatpak-session-helper.c	\
 	$(NULL)
 
-flatpak_session_helper_LDADD = $(AM_LDADD) $(BASE_LIBS) libflatpak-common.la
+flatpak_session_helper_LDADD = $(AM_LDADD) $(BASE_LIBS) $(OSTREE_LIBS) libflatpak-common.la
 flatpak_session_helper_CFLAGS = $(AM_CFLAGS) $(BASE_CFLAGS) $(SOUP_CFLAGS) $(OSTREE_CFLAGS) $(GSYSTEM_CFLAGS) $(JSON_CFLAGS) -DFLATPAK_COMPILATION
--- flatpak-1.0.1/portal/Makefile.am.inc.old	2018-08-08 16:56:20.000000000 +0200
+++ flatpak-1.0.1/portal/Makefile.am.inc	2018-09-12 13:23:54.795014399 +0200
@@ -34,6 +34,6 @@
 BUILT_SOURCES += $(nodist_flatpak_portal_SOURCES)
 CLEANFILES += $(nodist_flatpak_portal_SOURCES)
 
-flatpak_portal_LDADD = $(AM_LDADD) $(BASE_LIBS)
+flatpak_portal_LDADD = $(AM_LDADD) $(BASE_LIBS) $(OSTREE_LIBS)
 flatpak_portal_CFLAGS = $(AM_CFLAGS) $(BASE_CFLAGS) -DFLATPAK_COMPILATION
 flatpak_portal_CPPFLAGS = $(AM_CPPFLAGS) -I$(builddir)/portal