jenins grovy to call sh script

Question

Hi I have the following groovy script that I want to use to build a project in Jenkins

#!/usr/bin/env groovy

def deploymentPaths = '[]'

pipeline{
  agent {
    label 'jenkins-agent'
  }
  stages{
    stage('Build debug'){
        steps{
            sh './make_debug.sh'
        }
    }
  }
}

How can I make it wait till make_debug finishes and print its output? I tried

#!/usr/bin/env groovy

def deploymentPaths = '[]'

pipeline{
  agent {
    label 'jenkins-agent'
  }
  stages{
    stage('Build debug'){
        steps{
            def sout = new StringBuilder(), serr = new StringBuilder()
            def proc = './make_debug.sh'.execute()
            proc.consumeProcessOutput(sout, serr)
            proc.waitForOrKill(10000)
            println "out> $sout\nerr> $serr"
        }
    }
  }
}

But this doesn't work. Got following errors:

WorkflowScript: 13: Expected a step @ line 13, column 7.
            def sout = new StringBuilder(), serr = new StringBuilder()
         ^
WorkflowScript: 13: Expected a step @ line 13, column 39.
            def sout = new StringBuilder(), serr = new StringBuilder()
                                         ^
WorkflowScript: 14: Expected a step @ line 14, column 7.
            def proc = './make_debug.sh'.execute()
         ^
WorkflowScript: 15: Method calls on objects not allowed outside "script" blocks. @ line 15, column 13.
               proc.consumeProcessOutput(sout, serr)
               ^
WorkflowScript: 16: Method calls on objects not allowed outside "script" blocks. @ line 16, column 13.
               proc.waitForOrKill(1000)
               ^
WorkflowScript: 12: Missing required parameter: "delegate" @ line 12, column 5.
          step{
       ^
WorkflowScript: 15: Arguments to "error" must be explicitly named. @ line 15, column 13.
               proc.consumeProcessOutput(sout, serr)
               ^
WorkflowScript: 16: Expecting "class java.lang.String" but got "1000" of type class java.lang.Integer instead @ line 16, column 32.
               proc.waitForOrKill(1000)