ci: publish HPI from workspace, skip stash on built-in

unstash failed with EPERM on file timestamps after the Docker agent
wrote the artifact as root. Reuse the shared workspace instead.

Jenkinsfile

@@ -55,7 +55,6 @@ pipeline {
             sh 'mvn -B -ntp -DskipTests -Dset.changelist package'
             sh 'ls -la target/*.hpi'
             archiveArtifacts artifacts: 'target/*.hpi', fingerprint: true
-            stash name: 'hpi', includes: 'target/*.hpi'
           }
         }
       }
@@ -74,8 +73,8 @@ pipeline {
         }
       }
       agent { label 'built-in' }
+      options { skipDefaultCheckout() }
       steps {
-        unstash 'hpi'
         withCredentials([string(credentialsId: 'gogs-release-token', variable: 'GOGS_RELEASE_TOKEN')]) {
           sh '''
             set -euo pipefail