Previous patch breaks the build. Fix it.

Reported upstream at http://www.wand.net.nz/trac/libtrace/ticket/310
Index: configure.in
===================================================================
--- /configure.in	(revision 1701)
+++ /configure.in	(working copy)
@@ -98,6 +98,7 @@
 AC_SYS_LARGEFILE
 
 LIBPKTDUMP_LIBS="-ltrace "
+ADD_LDFLAGS="$ADD_LDFLAGS -L\$(abs_top_srcdir)/lib"
 LIBTRACE_LIBS=""
 TOOLS_LIBS=""
