bug: Jenkinsfile returns unknown characters if it contains Chinese characters.

[yeshan333]

reproduce Jenkinsfile content：

pipeline {
    agent any

    stages {
        stage('Hello中文>>>>>') {
            steps {
                echo 'Hello Worl中文
            }
        }
    }
}

validate result is:

Errors encountered validating Jenkinsfile:
WorkflowScript: 6: unexpected char: 0xB8 @ line 6, column 36.
                   echo 'Hello World'中�