windowsTestPathScript function
Exits 0 when path exists — as a directory, if directory — and 1 when
not (an error, being neither, exits otherwise).
Implementation
String windowsTestPathScript(String path, {bool directory = false}) =>
'if (Test-Path -LiteralPath ${_psq(path)}'
'${directory ? ' -PathType Container' : ''}) { exit 0 } else { exit 1 }';