Use git credential for pinned template engine install

Jenkinsfile

@@ -34,7 +34,9 @@ pipeline {
         }
         stage('Build') {
             steps {
+                withCredentials([sshUserPrivateKey(credentialsId: 'gitea-ssh', keyFileVariable: 'GIT_KEYFILE')]) {
                     sh '''
+                        export GIT_SSH_COMMAND="ssh -i $GIT_KEYFILE -o StrictHostKeyChecking=accept-new"
                         if command -v sudo >/dev/null 2>&1 && sudo -n true >/dev/null 2>&1; then
                             sudo apt-get update -y
                             sudo apt-get install -y python3-venv python3-pip make build-essential libpq-dev \
@@ -64,6 +66,7 @@ pipeline {
                     '''
                 }
             }
+        }
         stage('Lint') {
             steps {
                 sh '''