Fix build instructions

The missing submodule init / update caused build issues because the
external simple.css file could not be included.

1 files changed, 1 insertions, 0 deletions

diff --git a/README.md b/README.md
index c4a12d7..270e649 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,7 @@ On Linux Ceres can be build like this:
 ```
 git clone https://cgit.xengineering.eu/ceres
 cd ceres
+git submodule update --init
 make
 ```