Use $(LIBS_DIR) instead of assuming libraries will always be found in $(DIST)/bin.

Bug #114013 r=bryner,colin a=asa

xpinstall/src/Makefile.in

@@ -97,7 +97,7 @@ CPPSRCS		= \
 LOCAL_INCLUDES	= -I$(srcdir)/../public
 
 EXTRA_DSO_LDOPTS = \
-		-L$(DIST)/bin \
+		$(LIBS_DIR) \
 		$(EXTRA_DSO_LIBS) \
 		$(MOZ_JS_LIBS) \
 		$(MOZ_COMPONENT_LIBS) \