message: Add the $IsWindows workaround from the normal vcpkg scripts to the in-development script.
  This problem was discovered by ; many thanks to her in helping to run it down.
diff: @@ -26,7 +26,8 @@ if( $ENV:VCPKG_ROOT ) {
  $env:Z_VCPKG_POSTSCRIPT = resolve "${VCPKG_ROOT}/VCPKG_tmp_$(Get-Random -SetSeed $PID).ps1"
  [string]$vcpkgPath = "$PSScriptRoot/vcpkg"
  -if ($IsWindows) {
  +# The variable:IsWindows test is a workaround for $IsWindows not existing in Windows PowerShell
  +if (-not (Test-Path variable:IsWindows) -or $IsWindows) {
  $vcpkgPath += ".exe"
  }
  