Jenkins: Conditionally rebase on develop with build flag

Jenkinsfile.parameters

@@ -32,6 +32,8 @@ node ('macos1') {
       sh 'git checkout ' + BRANCH_NAME
       sh 'rm -rf node_modules'
 
+      sh 'test ${JENKINS_REBASE_DEVELOP} -eq 1 && git rebase origin/develop'
+
       // Assume all parameters are set in Jenkins 'Parameterized build'
       // TODO(oskarth): Consider read/write from .env to avoid having to specify in Jenkins again
       // sh 'cp .env.jenkins .env'