gradle clean in linux does not delete the contents of buildDir

Question

Gradle 2.13 Revision: 3b427b1481e46232107303c90be7b05079b05b1c OS: Linux 3.10.0-327.36.3.el7.x86_64 amd64

In linux on calling the clean task the contents of buildDir path are not deleted whereas the same in windows deletes the contents of buildDir(expected behaviour). Whats the reason ?

Code sample

apply plugin : 'java'
ant.importBuild 'build.xml'
sourceCompatibility = 1.8
def projVersion = ant.properties['version']
def projName = "xyz"
def buildPath = "/home/test/build"
def dependencyPath = "/home/test/dependency"
buildDir = new File("$buildPath","$projName")
def serviceDirBin = new File(buildDir , 'bin')
def serviceDirConf = new File(buildDir , 'conf')
def serviceDirThirdparty = new File(buildDir , 'thirdparty')

repositories    {
        flatDir {
            dirs file("$dependencyPath"),
        }
    }


sourceSets{
    main{
        java{
            srcDir 'src'
            }
        output.classesDir 'classes'
        }
    test{
        java {
            srcDir  'src/test'
              }
        }
}

dependencies {
    /*Some compile dependencies*/
}

jar{
    destinationDir = new File(serviceDirThirdparty, 'lib')
    baseName='xyz'
    manifest {

        'Build-Timestamp': new Date().format('yyyy-dd-MM HH:mm:ss'),
        'Specification-Version': '1.0',
        'Implementation-Version': "$projVersion"
    }
}

task xyzpackager << {

    copy{
            from ("$buildPath/sf/distribution/bin")
            into file(serviceDirBin)
        }
    copy{
            from ('conf')
            into file(serviceDirConf)
        }
    copy{
            from configurations.compile
            from configurations.runtime
            into new File(serviceDirThirdparty,'lib')
        }

}


test {
    reports {
        html.enabled = false
        junitXml.enabled = true


        junitXml.destination = file("TestReport/xml")
            }
}

jar.doLast {

            delete "$buildDir/tmp","$buildDir/dependency-cache","$buildDir/classes","$buildDir/libs"
        }
compileTestJava.doLast{
delete "TestReport"
}

the jar is copied to thirdparty folder and the bin/conf folders have some other files. SO basically i want to delete the buildDir before every new build