def dir = new File('myDir')

task createDir << {
    dir.mkdirs()
}

task copyFile(dependsOn: createDir, type: Copy){
    from myProperty
    into myDir
}

gradle -PmyProperty=myInputFile copyFile

task clean << {
    dir.deleteDir()
}

$ gradle clean

FAILURE: Build failed with an exception.

* Where:
Build file 'C:Userstempbuild.gradle' line: 41

* What went wrong:
A problem occurred evaluating root project 'temp'.
> Could not find property 'myProperty' on task ':copyFile'.

BUILD FAILED

task copyFile(dependsOn: createDir, type: Copy){
    from project.hasProperty['myProperty'] ? project.myProperty : ''
    into myDir
}