Add submodule notice to README.md

diff --git a/README.md b/README.md
index 703a9d8df703a9f55fd0ccb0e27974d4354fd634..6d21e4fc3abb739a9a5e535d621279b1c6eebb06 100644 (file)
--- a/README.md
+++ b/README.md
@@ -25,6 +25,12 @@ It's turing complete and somewhat useable.
 
 ## Invocation
 
+Make sure the submodules are checked out:
+
+```
+git submodule update --init
+```
+
 To build:
 
 ```