Update build.yml

Author: cuppajoeman

.github/workflows/build.yml

@@ -25,6 +25,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           submodules: recursive
+          ssh-key: ${{ CHECKOUT_SSH_KEY || '' }}
 
       - name: Install Conan
         uses: conan-io/setup-conan@v1