libtool: Enable hardening in libltdl

See the rhbz#1289759 and rhbz#1214506.  We disable hardening namely because
that bakes the CFLAGS/LDFLAGS into installed /bin/libtool and ltmain.sh files.
At the same time we want to have libltdl.so hardened.  Downstream-only patch.

---

diff --git a/Makefile.am b/Makefile.am
index 13dfc63..5c5603a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -309,10 +309,27 @@
 ## Libltdl. ##
 ## -------- ##
 
 include libltdl/ltdl.mk
 
+libltdl_libltdl_la_CFLAGS = $(CUSTOM_LTDL_CFLAGS)
+libltdl_libltdl_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+
+libltdl_dlopen_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+libltdl_dld_link_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+libltdl_dyld_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+libltdl_load_add_on_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+libltdl_loadlibrary_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+libltdl_shl_load_la_LDFLAGS  += $(CUSTOM_LTDL_LDFLAGS)
+
+libltdl_dlopen_la_CFLAGS  = $(CUSTOM_LTDL_CFLAGS)
+libltdl_dld_link_la_CFLAGS  = $(CUSTOM_LTDL_CFLAGS)
+libltdl_dyld_la_CFLAGS  = $(CUSTOM_LTDL_CFLAGS)
+libltdl_load_add_on_la_CFLAGS  = $(CUSTOM_LTDL_CFLAGS)
+libltdl_loadlibrary_la_CFLAGS  = $(CUSTOM_LTDL_CFLAGS)
+libltdl_shl_load_la_CFLAGS  = $(CUSTOM_LTDL_CFLAGS)
+
 lt_aclocal_m4	= $(srcdir)/$(ltdl_dir)/aclocal.m4
 lt_config_h_in	= $(srcdir)/$(ltdl_dir)/config-h.in
 lt_configure	= $(srcdir)/$(ltdl_dir)/configure
 lt_configure_ac	= $(srcdir)/$(ltdl_dir)/configure.ac
 stamp_mk	= $(srcdir)/$(ltdl_dir)/stamp-mk