Add RELRO to LDFLAGS.

Added linking flags to satisfy rpmgrill checks.

Change-Id: Ib2200bfbb78935eb1e74d960ad1fc0f84d25b5ab
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Bug-url: https://bugzilla.redhat.com/show_bug.cgi?id=1152878