For what I know there is no easy way to pass custom options to
avrdude via the Arduino IDE, but Sloeber (to which I'm a contributor) does.
Beware though, the
-F option of
avrdude command doesn't solve the problem, just forces to skip the device signature verification, but if your Attiny is returning such signature something else is wrong and you'll end up with a failed firmware upload anyway.
If the device was working and suddenly stopped it's more than probably a wiring issue, as already suggested in the comments. The second most probable cause, in my experience, would be a hardware issue: you might have accumulated some static charge and then touched the Attiny or any wire connected to it, destroying one of the ISP pins...
My bet is on the former: my experience with the latter is you get changing signatures in the form of
0xFFFFFF but, luckily for me, this didn't occur so often to accumulate a true knowledge.