Fix contrib/script build

Summary:
Fixes a missing line in https://github.com/caffe2/caffe2/commit/ff2c9735477e4d5076da4ddfc964eb0fd3c360bf

zdevito jamesr66a
Closes https://github.com/caffe2/caffe2/pull/1540

Reviewed By: bddppq

Differential Revision: D6448498

Pulled By: dzhulgakov

fbshipit-source-id: 997453fc6182910140967506d6ad2c8366d06e32
diff --git a/caffe2/contrib/CMakeLists.txt b/caffe2/contrib/CMakeLists.txt
index f571ece..be3f9d2 100644
--- a/caffe2/contrib/CMakeLists.txt
+++ b/caffe2/contrib/CMakeLists.txt
@@ -3,6 +3,7 @@
 add_subdirectory(nccl)
 add_subdirectory(nnpack)
 add_subdirectory(shm_mutex)
+add_subdirectory(script)
 # Finally pass the src lists back to the parent
 
 # CPU source, test sources, binary sources