With plugin version 1.8.12
With pipeline like:
pipeline {
	agent {
		label "master"
	}
	stages {
		stage('windows-msvc141') {
			agent {
				label "master"
			}
			steps {
				p4sync charset: 'utf8', credential: 'perforce', populate: autoClean(delete: true, modtime: false, parallel: [enable: true, minbytes: '1024', minfiles: '1', threads: '8'], pin: '', quiet: true, replace: true, tidy: false), source: depotSource(
'''//depot/Mainline/Generation_3/sources_ecwjp2v4/Source/BuildUtilities/sign/...
//depot/Mainline/Generation_3/tools/CodeSigning/signtools/...
//depot/Third_Party/gdal/gdal-2.3.0/...
//depot/Third_Party/IPP/8.2/Windows/...
//depot/Third_Party/LizardTech/MrSID/9.5.4.4709/MrSID_DSDK-9.5.4.4709-win32-vc15/...
//depot/Third_Party/LizardTech/MrSID/9.5.4.4709/MrSID_DSDK-9.5.4.4709-win64-vc15/...
//depot/Third_Party/swig/swigwin-1.3.31/...
//depot/Third_Party/maven/settings/settings-perth.xml
'''                            
				)
				bat '''
					rem build the component
				'''
			}
			post {
				cleanup {
					cleanWs()
				}
			}
 		}
	}
}
Our resultant workspace looks like:
What did I miss?
