check out submodules

Author: yuzawa-san

.github/workflows/build_cpp.yml

@@ -34,7 +34,8 @@ jobs:
     runs-on: 'ubuntu-latest'
     steps:
     - uses: actions/checkout@v2
-
+      with:
+        submodules: true
     - name: Install dependencies
       run: |
         sudo apt update

.github/workflows/build_matlab.yml

@@ -35,6 +35,8 @@ jobs:
     runs-on: 'ubuntu-latest'
     steps:
     - uses: actions/checkout@v2
+      with:
+        submodules: true
     - name: Setup MATLAB
       uses: matlab-actions/setup-matlab@v1
     - name: Compile mex wrappers 

.github/workflows/build_python.yml

@@ -35,6 +35,8 @@ jobs:
     runs-on: 'windows-latest'
     steps:
     - uses: actions/checkout@v3
+      with:
+        submodules: true
     - uses: actions/setup-python@v4
     - name: Install python deps
       run: |