The reason why it was originally introduced:arduino/Arduino@a6909bdWhy we are removing it now?* Windows does preserve the state of the RTS/DTR bits on successive  opening of the serial port.* The serial library used in the Arduino IDE 1.8.x has a bug when trying  to set DTR=false, on successive opening of the port the DTR line is  set back high by the USB serial driver. This works differently from  the serial library we use in the Arduino CLI, that sets DTR=false for  good and this change is preserved on the successive opening of the  port.* Having the serial port left in a state with DTR=false may cause  problems to tools uploading later.It may probably completely removed, but for now, to reduce the testingsurface, it will be disabled only for Windows.Co-authored-by: Cristian Maglie <c.maglie@arduino.cc>