All slashes in transfer commands on Windows are changed to backslashes

• the target system is Windows
• target_post_command=xcopy /Y "$TargetFileName" "c:\another\folder"
  then Jade calls

  C:\Windows\system32\cmd.exe /C xcopy \Y "\path\to\target\file" "c:\another\folder"
  

Save a cmd file on Windows (e.g. C:\TEMP\myxcopy.cmd) with the content

xcopy /Y "%~1" "%~2"

and use
target_post_command=C:\TEMP\myxcopy.cmd "$TargetFileName" "c:\another\folder"