gh: checkout also submodules

Signed-off-by: Alessandro Comodi <acomodi@antmicro.com>

.github/workflows/ci.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f03746d..a4b73b1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,6 +9,8 @@
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: recursive
 
     - uses: symbiflow/actions/checks@main
 
@@ -20,6 +22,8 @@
         python-version: [3.6, 3.7, 3.8, 3.9]
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: recursive
 
     - name: Setup
       run: |