jenkins: Sync submodules

Always sync submodules before the SCM step to handle coreboot adding
new submodules. This is needed because coreboot uses relative paths for
submodules, so git tries to clone it from the System76 GitHub
organization. We are not mirroring submodules and want to clone from
gerrit.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

Jenkinsfile

@@ -54,6 +54,11 @@ pipeline {
                 setBuildStatus("pending", "Pending")
                 slackSend(color: "good", message: "${env.JOB_NAME} - #${env.BUILD_ID} started (<${env.BUILD_URL}|Open>)")
 
+                sh """#!/bin/bash
+                    # Update submodule URLs because of coreboot
+                    git submodule sync --recursive
+                """
+
                 // https://www.jenkins.io/doc/pipeline/steps/params/scmgit/
                 checkout scmGit(
                     branches: [[name: '${SOURCE_BRANCH}']],