Add new subdirectory to LIBSUBDIRS.
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 24d364d..45a6d52 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -906,7 +906,7 @@
tkinter/test/test_ttk site-packages test \
test/decimaltestdata test/xmltestdata test/subprocessdata \
test/tracedmodules test/encoded_modules \
- concurrent concurrent/futures encodings \
+ collections concurrent concurrent/futures encodings \
email email/mime email/test email/test/data \
html json test/json_tests http dbm xmlrpc \
sqlite3 sqlite3/test \