Enable submodule checkout in build workflow

Author: YukariChiba

.github/workflows/build.yml

@@ -36,10 +36,11 @@ jobs:
           repository: ${{ github.event.inputs.gitrepo }}
           ref: ${{ github.event.inputs.gitref }}
           path: repo
+          submodules: 'true'
       - name: "Checkout remote repository (Remote)"
         if: contains(github.event.inputs.gitrepo, ':')
         run: |
-          git clone ${{ github.event.inputs.gitrepo }} repo
+          git clone ${{ github.event.inputs.gitrepo }} repo --recurse-submodules
           cd repo
           git checkout ${{ github.event.inputs.gitref }}
       - name: "Install dependencies"