Do not use BUILT_semphore to force rebuilds when re-run (#2593)

Remove the placement of the `BUILT_semaphore` file after the build in
the Jenkins Pipeline and force it to rebuild any changes after a PR is
re-ran.

ci/Jenkinsfile

@@ -149,7 +149,7 @@ pipeline {
                                                 }
                                             }
                                             sh(script: './link_workflow.sh')
-                                            sh(script: "echo ${HOMEgfs} > BUILT_semaphor")
+                                            //sh(script: "echo ${HOMEgfs} > BUILT_semaphor")
                                         }
                                     }
                                     if (env.CHANGE_ID && system == 'gfs') {