ADJ: midchain delegate to performing stacking

this can be used by e.g. tunnels so it doesn't need to be
implemented for each tunnel type.

Change-Id: I0790f89aa49f83421612b35108cce67693285999
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/CMakeLists.txt b/src/vnet/CMakeLists.txt
index 822ad68..8e56ac3 100644
--- a/src/vnet/CMakeLists.txt
+++ b/src/vnet/CMakeLists.txt
@@ -1371,6 +1371,7 @@
   adj/adj_nbr.c
   adj/adj_glean.c
   adj/adj_midchain.c
+  adj/adj_midchain_delegate.c
   adj/adj_mcast.c
   adj/adj_l2.c
   adj/adj_nsh.c